A Maritime Dictionary

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Ranger Hope © 2007- All rights reserved


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Code flag;       Diver below, keep well clear at slow speed.


Always afloat.


Always accessible - always afloat.

A flag + three numerals:

Code flags;     Azimuth or bearing.


When a wind hits the front of the sails forcing the vessel astern.


Toward the stern.

Abaft of the beam:

Bearings over the beam to the stern, the ships after sections.


To jettison cargo.

Abandon ship:

To forsake a vessel in favour of the life rafts, life boats.


Diminish, stop.

Able bodied seaman:

Certificated and experienced seaman, called an AB.


On the side of the vessel, amidships or at right angles.


Within or on the vessel.

About, go:

To manoeuvre to the opposite sailing tack.

Above board:


Able bodied seaman:

Advanced deckhand ranked above ordinary seaman.


Alongside.  Side by side


A plate reinforcing the top of a drilled hole that accepts a pintle.


A violent wind blowing off the South East Brazilian coast between May and August.


American Bureau of Shipping classification society.

Able bodied seaman


The dissipation of energy in the medium through which the energy passes, which is one cause of radio wave attenuation.




A deep chasm.

Abyssal, abysmal:

The greatest depth of the ocean

Abyssal gap:

A narrow break in a sea floor rise or between two abyssal plains.

Abyssal plain:

A level region at great depth in the ocean.

Access holes:

Holes cut in a structure to facilitate entry and exit.


Australian Communication & Media Authority

Acid rain:

The acidification of rain (largely resulting from atmospheric pollution from burning sulphur rich coal) causing forest die back and reduction of quality of water habitats.



A. class:

Australian vessel survey class, unlimited offshore.

A. class division:

Divisions made of steel or equivalent material, suitably stiffened and capable of preventing the passage of smoke and flame up to the end of the first 1 hour of the standard fire test.


The living quarters of a vessel.

Accommodation ladder:

Portable steps providing access from the vessel’s entry deck to the waterline.


A tank that smooths out pressure variability in a fresh water system.

A trap to remove water within a refrigeration system.


A term used to indicate that the anchor is clear of the hawse pipe and suspended above the water, ready for letting go.

A.C. current:

Alternating current is a form of pulsing electricity supplied by alternators. The voltage cycles between positive and negative at a regulated frequency (cycles per second measured in Hertz).


The process of deposition of material at the bottom of the oceans.

Build up of matter over a surface (e.g. ice on rigging, fouling on hulls).


Hooks for the chains.


Decorative finial for a post.

Adams, Joe

Australian prolific fast cruising yacht designer tragically murdered in his late years of life in New Guinea.


Address commission.

Added mass:

An effective increase in hull mass caused by the dragged water-flow during motion.

Added weight method:

A method used to determine a ship’s damaged stability by calculating a partial flooding as added weight rather than as lost buoyancy.


Occurring without heat.


Adjust, adjustment.


First or highest commander.

Admiralty brass:

Alloy of approximately 70% copper, 29% zinc. See Naval brass.


A vessel not attached to the wharf or an anchor.

Ad valorum:

A term from Latin meaning, "according to value."


The twin vectors of advance (headway/headreach) and transfer are the distance forward and the distance to the left or right that a vessel will make while negotiating a turn (its tactical diameter) or going full astern to avoid a collision (its stopping distance).


The horizontal air movement in the lower atmosphere due to difference in atmospheric pressure (wind).

Advection fog:

Fog resulting from warm air over relatively colder water.


Pertaining to the United Kingdom Naval Command.

Admiralty pattern anchor:

An older style anchor with crown, twin flukes and a stock perpendicular to its shank.


Shipwrights tool used to face timber (cut surface to shape).


A length of conducting wire that detects and/or over a band of similarly proportional radio wavelengths.

Aero lights:

Aids to navigation for aircraft.

Aeronautical drift (Da):

Drift caused by bailout trajectory or aircraft gliding distance.

Aeronautical position:

Initial position of a distressed aircraft at the time of re-entry, engine failure, aircrew ejection or bailout.


Aqueous Film Forming Foam

Affreightment contract:

An agreement by an ocean carrier to provide cargo space on a vessel at a specified time and for a specified price to accommodate an exporter or importer.


Supported by the surface of the water.


The largest dry bulk carriers.


African fine straight grained hardwood timber. Dark coloured, easily hand worked and acceptable for marine use.

Aft, after:

The stern end of a vessel.

After body:

A vessel’s sections aft of amidships.

Aft peak:

A compartment immediately forward of the stern post usually below the load water line.

Aft peak bulkhead:

The transverse bulkhead forward of the stern post, being the forward boundary of the after-peak tank that is required to be maintained as  watertight.

Aft peak tank:

The furthest aft  tank/compartment (used for fresh water or ballast).

After Perpendicular (AP):

A line which is perpendicular to the intersection of the after edge of the rudder-post with the designed load water-line. This is the case for both single- and twin-screw merchant ships. For some classes of warships, and for merchant ships having no rudder-post, the after perpendicular is taken as the centre-line of the rudder stock.

After rake:

The angle beyond vertical of the vessel’s overhanging stern structure.


Extreme aft end of a vessel.


African straight grained hardwood timber durable for marine use.


Australian geodetic datum.


Australian Geodetic Datum 1966 - the datum used by the Australian Hydrographical Office on Australian Charts which is a different datum used by the GPS. See also ‘WGS84’

Age of the moon:

The interval since the last new moon.

Age of the tide:

The interval since the last full/new moon and the next spring tide.

Agonic line:

A line joining points with no magnetic variation.


Touching the sea bottom.

Agulhas Current:

A warm Indian Ocean current running southward along the East African Coastline.


All going well.


Australian Height Datum adopted by the National Mapping Council for vertical control for mapping (mean sea level 1966-68).


Towards the vessel’s bow.


Used to attract the attention of another vessel.


Australian hold ladders.


Australian Hydrographical Office.


When a vessel lies perpendicular to the wave fronts.  A method of heaving to.


Admiralty information overlay.


A mixture of mainly nitrogen, with oxygen and carbon dioxide, constituting the atmosphere with races of inert gasses.

Air casing:

An upper deck combing surrounding the funnel stack to protect the deck from heat and assist fireroom ventilation.

Aircraft carrier:

A warship designed to carry planes.

Aircraft coordinator (A.C.O.):

A person who coordinates the involvement of multiple aircraft in SAR operations.

Air draught:

Height clearance of a vessel.

Aircraft glide:

Maximum ground distance an aircraft could cover during descent.

Air hammer:

Compressed air (nail or rattle) gun used to remove surface rust.

Air port:

A window to provide light and ventilation.

Air-purifying respirator:

A respirator with an air-purifying filter, cartridge, or canister that removes specific air contaminants by passing ambient air through the air-purifying element.

Air tank:

A tank that provides additional vessel floatation.

A tank of breathable air for underwater scuba divers.

Air tight door:

A fully sealed door that will exclude air from passing.


Automatic Identification System.


As low as reasonably practical.

Alaska current:

A warm North Pacific Ocean current running firstly Northward along the Alaskan Coastline then West into the Pacific.


Large wing spanned ocean wandering seabird, featured in the epic poem the Ancient Mariner.

Alden, John:

American early 20th century classic yacht designer, associated with N.G. Herreshoff.


Away from the direction from where the wind comes from.


See alert phase.

Alert phase:

A situation wherein apprehension exists as to the safety of an aircraft or marine vessel, and of the persons on board.

Alerting post:

Any facility intended to serve as an intermediary between a person reporting an emergency and a rescue coordination centre or rescue sub-centre.


To assemble a shaft in line with its bearing to minimise wear and vibration.


A command to be quicker with the task.


The trade winds.


A compound that is chemically opposite to acid.

The electrolyte in Ni-Cad batteries of dilute potassium hydroxide.

All fours mooring:

Anchoring a vessel with two chain cables ahead and two chain cables astern.

All hands:

All the crew.


The act of striking or collision of a moving vessel against a stationary object (American).



All standing:

To come to a sudden stop.


Up the mast or In the rigging.


Berthed against a wharf or jetty.

Allotment note:

Traditional payment option for a seaman to dispose of some of his pay to relatives.


Articulated loading platform; a partially buoyant tower rising from a universal joint on the sea floor and used for berthing and loading at oil platforms.




A step in a graving dock.


A device consisting of a spinning magnet within a series of coils that produces AC electrical current, subsequently rectified to DC when used for charging vessels batteries.


Lightweight corrosion resistant metal used for fittings and hull plating.

Aluminium bronze:

Alloy of approximately 90% copper and 10% aluminium.


Amplitude modulation.


The outboard hulls of a trimaran.


Australian Maritime College.

American bureau of shipping:

American ship classification society.


The centre of the vessel, with reference to her length or breadth.


An instrument that measures the amount of current, in amperes, in an electrical circuit.


A unit of electrical power and abbreviation of ampere.


Ampere or amps are the unit of electric current. Amps can be compared to the volume of water flowing through a water pipe.

Amps = Volts ÷ Ohms


Ancient Greek consort of Poseidon, God of the sea.


An ancient earthenware vessel used to transport liquids.


As in making sound louder or a radio wave stronger.

Amp meter:

See Ammeter:


The maximum power of a radio wave.

The bearing of a heavenly body expressed in the degrees towards the North or South Pole from East or West sighted at its rising or setting. For example, amplitude E20ºN = 90º - 20º = 70º, W20ºN = 270º + 20º = 290º.  See azimuth.

Amplitude modulation:

The varying of amplitude to the radio carrier wave to enable encoding for the simulation of audio messages.


Australian Maritime Safety Authority.


Automated mutual-assistance vessel rescue system.


Analogue display, one that uses physical quantities (e.g. length or deflection) to represent numbers.


A device that holds the vessel to the sea bottom.


A place to anchor.

Anchor bar:

A lever used to work an anchor windlass.

Anchor billboard:

A deck housing to stow an anchor.

Anchor buoy:

A small buoy used to mark the position of the deployed anchor.

Anchor chain:

Secures the anchor to the ship and ensures that the pull on the anchor is horizontal thus embedding the flukes under tension. Hence the phrase, “a vessel anchors by its chain”.

Anchors in tandem:

Use of two anchors in a line to improve holding power.

Anchor light:

A white light hoisted while anchored, also known as a riding light.

Anchor rode:

A length of anchor line.

Anchors aweigh:

Announced when the anchor just clears the bottom at retrieval.

Anchor stopper:

A device to lock off an anchor chain.

Anchor watch:

A lookout posted to safeguard the vessel while at anchor.

Ancient Greece winds:

Northerly -  Boreas

Easterly -    Eurus

Southerly -  Notos

Westerly -   Zephyrus


An instrument that measures wind speed.


See angle bar.

Angle bar:

Steel section of L shaped profile.

Angle clip:

A short length of angle bar.

Angle collar:

A ring in angle bar section used to seal a pipe passing through a deck or bulkhead.

Angle of cut:

The lesser angle between two position lines.

Angle of dip:

The angle that the north end of a compass needle is inclined from the horizontal, being downward in the Northern Hemisphere (positive) and upward in the Southern Hemisphere (negative).

Angle of incidence:

The angle that a wave or electromagnetic radiation strikes a surface.

Angle of indraft:

The angle at which the wind crosses the isobars. It results from a balance of pressure gradient force, coriolis force and friction. The angle of indraft varies from approximately 45° at the edge of a storm to 0° in the eye of a cyclone.

Angle of reflection:

A deflection of direction of a wave or electromagnetic radiation directly opposite to its angle of incidence.

Angle of refraction:

A deflection of direction of a wave or electromagnetic radiation due to its encountering a changed density of material.

Angle of repose

The natural slope that a loose pile of grain, sand, coal, etc will rest at.


Chemicals without crystalline water.


A less-noble metal of an electrolytic cell where corrosion occurs.  It may be on the surface of a metal or alloy.  The more active metal in a cell composed of two dissimilar metals, or the positive electrode of an impressed-current system. Sacrificial anodes of zinc or aluminium are fitted to vessels to reduce corrosion from more valued components.


An occurrence that is not typical.


The opposite to temper. When metal bends it becomes brittle (work hardened). The annealing process is one of heating the metal to cherry red then plunging it into lime and allowing it to cool slowly to remove brittleness.


The positive terminal of an electrical circuit.

A sacrificial anode is a consumable zinc bar used to electrochemically corrode in preference to any nearby more galvanic noble metals of a vessel’s underwater structures. 


Australian National Tide Tables.

Antarctic circum-polar current:

An Easterly setting current situated North of the Antarctic sub-polar current.

Antarctic sub-polar current:

A Westerly setting current along the continental edge of Antarctica.


See aerial.

Antenna gain:

A measure of the effectiveness of an aerial.


See high pressure system.


An additive to an engine’s fresh water coolant that protects against freezing and consequent damage resulting from expansion.


Paint coating on the bottom of a boat to prevent marine fouling.  Traditionally copper sheet was used.

Anti-sea clutter:

A radar operational control that limits the return of echoes from nearby waves around a vessel, thus allowing ship targets to be more apparent on the radar screen.

Anti-siphon valve:

A valve allowing air ingress to a liquid filled line, thus limiting siphon action development.

Anti-trip chine:

A flared out aft section of the side/bottom of the boat. The purpose is to prevent the hard chine of the boat catching a wake or small wave on a sharp turn.


See after perpendicular.

Apparent temperature  heat index (AT):

The AT index used by the Australian Bureau of Meteorology is based on a mathematical model of an adult, walking outdoors, in the shade. AT is defined as the temperature, at the reference humidity level, producing the same amount of discomfort as that experienced under the current ambient temperature and humidity.


See classical winds.


The space provided for the propeller.


The time or position at which a planet is farthest from the Sun.


See classical winds.


Animal and plant health inspection service.


American Petroleum Institute


The point in the orbit of the Moon which is farthest from the Earth.

Apparent coefficient A:

A constant compass error due to reasons other than the ship’s magnetic structure such as compass card/sighting alignments.

Apparent wind:

The resultant of the actual wind and the wind caused by the boat’s motion.  As the boat moves faster, the more the apparent wind moves forwards.


The waterways that give access or passage to harbours and channels.


A timber fixed behind the stem that acts as a surface to which the forward ends of the planking can be nailed.


Farming of marine plants or animals.


A breathing apparatus for divers consisting of compressed air tanks and regulator.


Relates to water.


An artificial channel for the conveyance of water usually elevated.


A covered passage naturally cut through a headland.


The study of historical artefacts.

Archimedes' principle:

A body floating in water experienced an upthrust equal to the weight of water it displaces.


A sea studded with many islands.


A Spanish fleet of men-of-war.


The rotating electrical windings of a generator or motor.


Automatic radar plotting aids.

Arc of visibility:

The sectors in which a light is visible from at sea.

Arctic smoke:

Fog resulting from cold air over relatively warmer water.


See classical winds.


A satellite-based location and data collection system.


Biblical vessel built by Noah for the creatures of the world to survive the flood.

Arming the lead:

Placing tallow in the recess in the bottom of the sounding lead to ascertain the nature of the sea bed.


The historic naval shipbuilding yard in Venice.


A small square sail set on the bowsprit.


See Articles of agreement below.

Articles of agreement:

The document containing all particulars relating to the terms of agreement between the master of the vessel and the crew. Sometimes called ship's articles, shipping articles

Artificial horizon:

A horizon produced by bubble, gyro, or mercury trough to allow measurement of altitude of celestial bodies.

Artificial respiration:

Historic term for EAR.




European fine straight grained hardwood timber. Light coloured, flexible, easily steam bent but not durable for marine use. Commonly prized for coachwork and craft machinery.

Ashcroft system:

Timber boat building technique using two layers of overlapping diagonal strip planks with glue barrier between. High strength and low weight.


Squared hewn stone; as in walling.


The radar displayed angle between the direction a target is heading and your ship, which is at the centre of the display.

Aspect ratio:

The length of the leading edge of an aerofoil of hydrofoil as compared to its width. Luff and foot of a sail.


Towards the stern.  The opposite of ahead.

Astronomical Twilight:

The period from Nautical Twilight to the moment when the sun's centre is 18º below the horizon in the evening, and from the moment when the sun’s centre is 18º below the horizon in the morning to the beginning of Nautical Twilight in the morning.


Along track error.




Across the vessel from side to side.


Mythical ancient civilisation whose lands were devoured by the sea.


The mix of gases immediately surrounding planets.

Atmosphere-supplying respirator:

A respirator that supplies the respirator user with breathing air from a source independent of the ambient atmosphere, and includes supplied-air respirators (SARs) and self-contained breathing apparatus (SCBA) units.

Atmospheric pressure:

The pressure or weight of a column of air at a specified elevation on the earth, being an average of 14.7 psi at sea level or 1000 hecto-pascals (millibars).


A ring-shaped coral reef which has islands on it.


A small atoll on the margin of a larger one.


Loss of power in a radio wave typically due to absorption, scattering and reflection over an extended distance of propagation.


A spiral shaped drilling bit, usually long.

Aurora borealis:

Fantastic light show in the Arctic and Antarctic skies produced as solar rays pass through the earth’s magnetic field.


Australian Search and Rescue Authority.


An electro-mechanical device that can be activated to provide automatic steering over-ride.

Australian coastal and middle-water operations:

Operations within a range laterally along the coast within a limit of 600 nautical miles to seaward; or within such lesser limits as may be specified.

Australian Height Datum:

See AHD.


An instrument to steer a vessel automatically.


The winches, pumps, motors, etc. of a ship but not its main propulsive machinery.

Auxiliary engine:

An engine, outboard or inboard, used to power a sailboat.

Auxiliary machinery:

A ship’s machinery other than its main engines.


Mythical ancient British island and burial place of King Arthur, claimed to be the once lake bounded mount, Glastonbury Tor.




Small, fast messenger ship, Spanish 16th century.

Awareness range:

Distance at which a search scanner can first detect something different from its surroundings but not yet recognise it.

Awareness stage:

A period during which the SAR system becomes aware of an actual or potential incident.


Partially covered by water.


To raise the anchor.


Cloth suspended overhead for shade or against rain.

Awning deck:

See hurricane deck.


Automatic Weather Station.

Aye, Aye:

I understand and will comply with the order.


The bearing of a heavenly body expressed as the degrees East or West of the poles (the distance from North or South). For example S20ºE = 180º- 20º = 160º, N20ºW = 360º- 20º = 340º. See amplitude.

Azimuth ring:

A sighting instrument set over the ships compass to facilitate taking bearings.

Back to top



Code flag; I am loading, carrying or discharging dangerous cargo.

Sound signal;   Last barge of a tow in restricted visibility.


Soft white metal alloy used for shell type engine bearings.


Seagoing three masted Carib vessel.


To force a sail against the wind when manoeuvring (a jib is ‘backed’ when you want to force the bow to fall off); swing away from the wind.

Back, backing:

The wind backs when it shifts in an anti-clockwise direction.


A reciprocal bearing to the vessels course.


The stem, keel, stern post & transom set up for timber building.

Back flooding

Occurs when fluid passes in reverse through a pump or valve back into the fluid reservoir or compartment.

Back freight:

The owners of a ship are entitled to payment as freight for merchandise returned through the fault of either the consignees or the consignors.

Back haul:

Moving cargo on the return leg of a voyage for the purpose of minimizing ballast mileage and reducing transportation costs.

Back pressure:

A resistance in a pipe-line that restricts the forward flow movement.


Hawsers laid out as forward springs or after springs to reduce surging when at a berth.


Rigging supports from the masthead to reduce forward bending when the force of the wind is from astern.


Waves reflected back to sea from the shoreline.


Wind deflected from a sail affecting flow over another.


Bunker Adjustment Factor. The fuel charge adjustment to balance market price for bunkers.

B. class:

Australian vessel survey class, for 200NM offshore.

B. class division:

Divisions made of incombustible material and capable of preventing the passage of smoke and flame up to the end of the first ½ hour of the standard fire test.

Baffle plate:

A perforated partition in a tank to limit the surge of liquid as a boat moves.

Bagged cargo:

Commodities usually packed in sacks or in bags, such as sugar, cement, grain, etc.


Padding of old rope, rubber or canvas wrapped round stays to prevent chafe on the sheeted out sails.


To scoop water out of a craft.


Container used to scoop water out of a craft.

Balanced frames:

A steel ship’s midship frames that are of an identical square flanged shape.

Balanced rudder:

A rudder design where the pivot point and the centre of its area meet, reducing the effort needed to turn it.

Bale capacity:

Hold cargo capacity from inside frames or ceiling.

Ball valve:

A valve consisting of a pierced internal sphere that opens/closes flow by rotation to become in line with/opposed to a pipelines input and output flow.


Heavy material (iron, lead, or stone) placed low in a vessel to improve stability.

Sea water pumped into and out of tanks placed low in a vessel to control stability.

Ballast ground:

Area that ships can discharge solid ballast material.

Ballast keel:

A heavy keel that improves stability.

Ballast tanks:

Tanks in a ship deigned to be flooded from the sea to maintain the stability of the ship as fuel and stores are expended.

Ballistic deflection:

The effect on a gyroscope caused by the change of course of the vessel.


A square length of timber substantially dimensioned (e.g.100-300mm)

Baltic moor:

To anchor to leeward by twin lines to the one anchor placed abeam, hence holding the vessel off a light duty jetty.


A shallow area of sea or river.


A Newfoundland fishing boat or fisherman.

Banks, Sir Joseph:

Botanist and patron of Captain Cook’s 1770 exploratory expedition of the South Seas.


A shallow entrance across the mouth of an inlet.

Barber hauler:

Tackle with an adjustable length of line on a jib sheet to trim its set.


Cylindrical protective wall around the gun turret stool, shell stowage and hoisting gear between a warship’s deck to the turret shelf plate.


The hire of a vessel without supply of crew, fuel or stores.

Bareboat charter:

A bareboat charter owner leases the ship and manages only its technical and trading operations. See bareboat.


When a vessel she has no sails set.


A flat bottomed cargo transporter, often without independent propulsion.

An admiral’s ship’s boat in the navy.


A bluff bowed 18th century single main deck, three masted trading vessel such as Captain Cooks “Endeavour”.


A shellfish that attaches to rocks and vessels’ bottoms.


An instrument that measures atmospheric pressure.


A three or more masted sailing vessel, square sail rigged on all masts.


A three or more masted sailing vessel, square sail rigged on fore mast and fore and aft rigged on after masts.


A crime by the master or mariners of a vessel contrary to their duty to the owners, whereby the latter sustain injury. It may include negligence, if so gross as to evidence fraud.

Barrel bow:

Planks curved around the bow as a nose.


Keg, small barrel.

Bascule bridge:

A counterweighted opening bridge.

Base line:

A horizontal line used in ship plans, drawn the length of the ship at greatest draught of the keel, from which heights are measured.


American flat bottomed construction scow.


An instrument used to measure depth.


Science of the measure of marine depths.


See Bathysphere.


A submersible built to withstand the pressures of ocean depths.


A piece of wood /plastic inserted in a sail leech pocket to stiffen the roach.

A strip of wood covering a seam in hull planks.

Batten down:

Secure hull openings due to imminent heavy weather.

Battens, cargo:

Strips of steel or timber used to stop cargo from shifting.


An electrochemical device that stores electric current, often specialised as a cranking battery (for starting the engine) and house battery (for powering lighting and utilities), the latter often being the deep cycle type (capable of repeated full discharge and recharge with minimal degradation).

The traditional wet cell lead acid battery (with dilute sulphuric acid as the electrolyte) is being increasing replaced by the newer maintenance free gel cell batteries.

Technological advances from lead acid batteries include alkaline (ni-cad) and lithium electrolyte based batteries.

Battery isolation (switch):

A single pole (positive conductor) or preferably double pole (positive and negative conductor) main cut off switch.

Battery sensed:

A voltage regulator that monitors the battery rather than the alternator.


Very large and heavily armoured warship.


Southern USA term for a waterway.


Before breaking bulk.


Both dates inclusive.


Bunker delivery note.


A person who collects objects washed ashore.

An out of work seaman.


Width, generally the widest point on the hull.

Beam knees:

Braces that join the deck beams to the frames.

Beam line:

A design line corresponding to the top of the frames.

Beam plate angle:

A beam made from flat plate bent into an L section.

Beam shelf:

In timber vessel construction, a longitudinal stringer that supports the deck beams.


The angular width of a radar beam, horizontal or vertical, the power of which is measured at the half power points.

Beam wind:

A wind from over the side of a vessel.


The direction of a point of interest.  To bear down on a vessel is to approach her from the windward.  To bear up is to approach from leeward.

Bear away:

Steer further away from the wind.

Bearding line:

In ship design and construction, the line of the inside of the planking and the side/face of the stem, keel, after deadwood and stern post. See Rabet.

Bear down:

To approach or come up to.


A supporting foundation.


The direction of an object usually referred to a compass.

The static meeting surface that supports a revolving shaft.

The bearings of a vessel are that part of her hull which is on the water line when she is at anchor and in her proper trim.

Bearing race:

In a roller bearing unit, the component that is the set of ball bearings and their ringed cage.

Bearing tube:

The pipe carrying a propeller shaft.


Going toward the direction of the wind, by alternate tacks.

Beaufort, Admiral Francis:

19th Century Surveyor and Hydrographer to the British Navy and developer of the wind scale bearing his name.

Beaufort scale:

Divisions of wind speed from Force 0 (calm) to Force 12 (Hurricane) with a visual description of the corresponding sea state-summarised below:

F0    Calm                   0kts Smoke rises vertically, sea as a mirror

F1    Light air           1-3kts Smoke moves, glassy sea

F2    Light breeze    4-6kts Rippled sea, windvanes move

F3    Gentle breeze 7-10kts Wavelets, light flags are extended

F4    Mod. breeze  11-16kts Small waves, some white horses

F5    Mod. breeze  17-21kts Mod. waves, many white horses

F6    Strong wind   22-27kts Large waves, foam, spray

F7    Near gale       28-33kts Sea heaps up, blown foam streaks

F8    Gale               34-40kts Mod. high waves, foam & spindrift

F9    Strong Gale   41-48kts High waves, toppling crests

F10  Storm             48-55kts V. high overhanging white waves

F11  Storm              55-63kts Exceptionally high waves, sea of froth

F12  Hurricane            >64kts Sea and air undistinguishable


Lack of wind.


A piece of rope placed so as to confine a spar or another rope.  A handle made of rope, in the form of a circle; the handle of a chest is called a becket.

Bedding compound:

Flexible composition to isolate the bottom of a fitting from its deck foundation in order to seal from moisture or corrosion.

Bed plate:

A series of transverse girders and longitudinal members that distribute engine and crankshaft bearings weight and stress over ship’s structure.


Support for tanks or engines.


European and American straight grained timber good for bending but not durable for marine use.

Australian Antarctic Beech much sought after for ships decking.

Before the wind:

When a sailing vessel has the wind coming from over the stern.


Biological exposure index.


To fasten a line by turns around a pin.

Belaying pin:

Wooden, steel or bronze pin that fits in a hole in a rail and is used to belay.


Under the deck.


Struck every half hour after each change of watch of four hours. 8 bells at change of watch, followed by 1 bell at half hour after change, 2 bells at + one hour, 3 bells at + one and a half hours, 4 bells at + two hours, etc.

Bell suction:

A flared end of a liquid cargo pipeline positioned close to the bottom of the tank.


Reinforcing outer plank layer in timber vessel construction.

Belly strap:

A sling positioned around the centre of a barrel or ships boat.


Ship aground above the next high tide level, awaiting the return of an increasing tidal cycle to enable re-floating.


Where one rope is made fast to a loop of another. To make fast.  To bend a sail is to make it fast to a spar.  To bend a cable is to attach it to an anchor.

Bending roller:

Machine that forms curved steel plate by passing over three offset rollers.


The gear drive (pinion) on a starter motor.

Benguela current:

A cool or warm South Atlantic Ocean current setting Northward along the Southern African West coast.


Short for steam bent timber component, frames, timbers, ribs or floors.

Bent on:

Describes an object tied on by a bend.


Best environmental practice.


A shelf along the upper edge of the beach thrown up by storm waves.

Bermudan, Bermudian rig:

A mainsail hoisted to the masthead and having a pointed top, with no additional spars near the head.

Bermudan sloop:

Single masted vessel with a Bermudan rig.


Where a vessel lies to anchor or mooring.

The place in a vessel where a person sleeps.

Between decks:

The space between the decks of a ship.


An angled cut or section in construction.

Bevel gear:

A gear configuration that directs a driveshaft through an angle of 90 degrees.

Bibby alleyway:

A passenger vessel’s passageway that is a cul-de-sac.




Where a rope folds over itself.

An indentation in the coastline.


Historic French term for a smaller vessel limited to coastal passages - Spanish, balandra, English, billy-boy.


The lowest sections inside a vessel’s hull.

Bilge blocks:

Supports for the lower plating/underneath of a vessel in dry dock.

Bilge blower:

A device for removing/replenishing air in a bilge.

Bilge bracket:

Strengthening plate beneath side frames between inner and outer bottoms.

Bilge keel:

A minimal keel fastened to the turn of the bilge to minimize roll or improve sailing performance with shallow draft vessels.

Bilge pump:


Bilge plates:

Shell plating at the turn of the bilge.


The point of a fluke on an anchor.

A narrow coastal promontory.

Bill hook:

A hooked bladed long handled tool for cargo (bales) work.

Bill of lading:

Document issued by a ship carrier to the shipper as evidence of their contract.


Historic name for English North Coast small coastal clinker fore and aft sailing vessel.


A casing for the ship’s compass, correction magnets and light.


Life forms that emit light.

Biro klasifikase Indonesia:

Indonesian ship classification society.

Bitter, or bitter-end:

The inboard end of an anchor cable secured to the bitt, or below decks, to some strong structural member.


Structures on which to secure mooring lines.


A tar based surface coating and waterproofing sealant used on a vessel’s rust or leak prone structures.


Notoriously evil but unsuccessful 18th century Welsh pirate, Captain Edward Teach.

Black cargo:

Cargo banned by general cargo workers because the cargo is dangerous or hazardous to health


The engineering crew.


The flat part of an oar that is immersed in the water.


A vessel to windward sail’s that interrupt the airflow of another’s that is downwind.



Prolonged; of six to eight seconds duration.

Short; of up to two seconds duration.

Bleed or bleeding:

A process of removing air from fluid lines or pipes.


Draining plug holes for a vessel when slipped.


Bulk liquids and gasses.

Bligh, Captain William:

18-19th century British Naval officer, renowned for the Mutiny on his vessel the Bounty, and the epic open boat sea voyage of the castaways that against all odds reached safe haven.

Blind arc:

An area totally shielded from radar transmissions by part of the ship’s structure.


Snow storm.


A pulley system enclosed in casing that is used as part of a system of mechanical purchases, called a tackle.

Block coefficient (CB):

A measure of the fullness of the form of the ship and is the ratio of the volume of displacement to a given water-line, and the volume of the circumscribing solid of constant rectangular cross-section having the same length, breadth and draught as the ship.

CB= ÷ (L x B x T)

The LPP is normally used in calculating the value of CB which varies with the type of ship.

Fast ships                         0.50-0.65 (fine form)

Ordinary ships                   0.65-0.75 (moderate form)

Slow ships                          0.75-0.85 (full form)

Blocking diode:

A electrical valve that permits charging of two batteries from one charger without paralleling the batteries.


Escape of gasses past the piston rings or valves during an engines work cycle.


A fan for compartment ventilation or engine aspiration purposes.

Blue gum:

Australian hardwood timber, durable for marine use with larger straight components, i.e. keel, sawn frames, etc.

Blue peter:

Code flag P, indicating a vessel’s imminent departure.


Print out of plans.


A navy personnel’s blue uniform.


A bow which is full and square.

A headland with a perpendicular face.


Best management practice.


Bridge navigational watch alarm system.


The distance a vessel travels on one tack.

Stern-board: When a vessel goes stern foremost.  By the board.  When the masts of a vessel fall over the side.


Blocks and tackle for hoisting a boat onto its davits.

Boat hook:

A hook and pole for picking up mooring buoys or objects in the water.

Boatswains chair:

See bosun’s chair.


Used to brace the bowsprit from its outboard end to the stem or cutwater near the waterline.

Body plan:

Elevation of the transverse sections of the hull. Usually drawn in two halves, from amidships to bow on one side and from amidships to stern on the other.

Boiler casing:

A partition that insulates the heat of a boiler.


Steam generating units used aboard ship to provide steam for propulsion (and) for heating and other auxiliary purposes.

Steam generating units used to heat timbers in bent construction.


A quick method applied to timber in order to make it supple for bending.


An upright round post with projecting arms, for belaying and snubbing dock or anchor lines.

Bollard pull:

The rated force that a tug boat can apply to a tow line.

Bolster plate:

A doubling protective plating around the entry of the hawse pipe.


The rope which goes round a sail, and to which the fabric is sewn.

Bomb ketch:

Historic sailing vessel equipped with mortars.


The electrical joining of all significant metals components on a boat.

Bonding conductor:

A normally non-current-carrying conductor used to connect the non-current-carrying metal parts of a boat and the non-current-carrying parts of the direct current devices on the boat to the boat’s common ground point for purposes of reducing hazards of stray-current corrosion, lightning and accumulated static, and to reduce radio noise.


Items attracting customs and excise taxation that must be imported through a bond port (first port of call) and may be stored in a bonded warehouse.


The addition of another sail.

Booby hatch:

A small hatchway, typically to a forecastle.


A spar used to extend the foot of a sail.

Floating barrier to limit passage of enemy vessels or pollution.

Boom crutch:

An upright, usually of wood, with a padded cradle on the top where the boom is rested; it is held in place by sockets and removed after the sail is hoisted.


A spar projecting from the stern to which is attached a backstay or sheet.

Boom table:

A platform around a mast’s base to support the heels of several booms.

Boom top:

A stripe painted around the hull above the waterline, separating the bottom paint from the topside finish

Boom vang:

Tackle system to prevent a boom from rising, or to tension the lower edge of a mainsail.

Boot top:

A painted line, just above the waterline.


Northerly wind blowing off the Slav Coast and into the Adriatic Sea.


To drill a hole.

The large tidal range of some river estuaries can create this tidal wave at the start of the incoming spring tide.


Northerly, later north nor’east wind of ancient Greece. See classical winds.


The centre of a propeller from which the blades radiate.

The stern frame’s propeller shaft aperture.

Boss plate:

A reinforcing plate at the stern frame’s propeller shaft aperture.

Bosun, boatswain:

The highest rating deck crew who is the supervisor of deck hands and is under the direction of the master or mate.

Bosun’s chair:

A seat to hoist a man aloft. The ropes should pass underneath the seat, so that if it breaks the he is still supported.

Bosun’s locker:

A store for repair materials for hull, sails and rigging.

Bosun’s pipe:

An ancient palm held tin whistle used for signalling orders aboard ship, consisting of a flat plate (keel) supporting a bent pipe (gun), terminating with a blow hole (orifice) at a hollow sounding sphere (buoy). Still used in the Navy to pipe dignitaries aboard a ship.

Bottle screw:

A device that applies tension to ropes or wires by the use of opposing screw threaded terminals tapped into a central frame.

Bottom plating:

A vessel’s underneath sections of shell plating.

Bottom shape:

As it affects performance in a planing boat. Maximum speed will be achieved when the bottom of the boat that forms the planing surface is flat. When the planing surface is a vee, the boat will have a softer ride but less potential speed, and will take longer to come up on a plane. A "flat bottom" makes a better "drag" boat; a deep vee will be a better rough water boat.


The destination or condition of vessel (outward bound, fogbound).

Boundary cooling:

The process of cooling down the area near the fire to stop its spread.

Bounding bar

A steel bar connecting a bulkhead edge to a tank top


The front of a vessel, forward.

Bow door:

Door at the vessel’s bow to facilitate the loading/unloading of vehicles.

Bower anchor:

The main anchor stowed in the hawse or at the bow.


A voracious freshwater fish, American.


A knot tied to form a temporary eye that will not slip.

Bow line:

A mooring line attached to the bow of a boat.

Bowline in a bight:

A knot tied in the middle of a line to form two loops that can be used as a temporary harness.


To fasten tightly together.

Bow shackle:

A shackle with a rounded bow, suitable for attaching multiple chains.


A spar forward of the stern.

Bow stopper:

A device fitted to the deck ahead of the windlass, to prevent the anchor chain from moving out on its own, or to take the strain off the windlass when the vessel is riding to its anchor.

Bow thruster:

A transversely positioned propeller at the bow of a vessel used to assist in manoeuvring.

Bow wave:

A continuing wave created on each side of the bow when the boat moves.

Bow and buttock lines:

Longitudinal sections of a boat, taken parallel with the centre-line at fixed intervals.


Fine grained European hardwood shrub tree used for pulley sheaves. Also used for making patterns (for castings).

Box the compass:

To box the compass is to name the thirty-two points of the compass in order.


Rope or wire rigged to a spinnaker pole to control its fore and aft position.

Tackles to trim square sail yards of sailing ships.


To haul a sail tight against its yard.


The ropes used to haul a sail tight against its yard.

Brake horsepower (BHP):

A unit of power, numerically equivalent to a rate of 33,000 foot-pounds of work per minute.


A plate used to stiffen angled joins of structural members, typically across the bilge turn in side frames or between beams and beam shelf.

Brackish water:

Fresh water mixed with sea water.


Alloy of copper & zinc. See Naval brass and Admiralty brass.


To join by heat using a hard solder (spelter), typically of brass or bronze.

Brazil current:

A warm South Atlantic current setting Southward along the South American Eastern coastline.

Brazilian mahogany:

Superior South American red lustrous timber with good workability and marine durability. Historically called logwood and also used for red/brown dye.

Breadth moulded (B):

This is the maximum beam, or breadth, of the ship measured inside the inner shell strakes of plating, and usually occurs amidships.

Breadth extreme (BE):

This is the maximum breadth including all side plating, straps, etc.


A discontinuation of a sheer line, for instance the break of poop or forecastle profile being higher than the waist’s deck line.

Break bulk:

Loose itemized units of cargo.


A breaking waves.

A small water cask.

Breaker points:

Contacts which open and close within a distributor, sending an electrical impulse for a spark from the high-tension ignition coil of an engine.


Waves that collapse creating white water, often along the shoreline.

Break ground:

When an anchor first lifts off the sea floor during retrieval.

Breaking sea:

As above but at sea, also called white horses.

Break out:

To release something out of stowage.


Raised section of a sailing dinghies foredeck to shed water from over the bow.


De-scaling the fouled underwater sections of a hull with a blow torch.

Brest beam:

The beam nearest to midships of the poop and forecastle deck.


A horizontal knee behind the stem, to securing the bow and wales.

Breast lines:

Mooring lines to control the vessel from swaying.

Breast rail:

The top rail of a balcony on the quarter deck.




Southern Australian desert hot and dry wind experienced in summer.


An upper room on a large vessel fitted with the controls for driving, navigating, communications and keeping watch.

Bridge house:

An upper deck superstructure of officer’s accommodation and staterooms..

Bridge rectifier:

An arrangement of diodes (electrical one way valves) that rectify DC current to AC current, often positioned within a heat sink casing to limit excessive temperature build up. 

Bridge wing:

Port and starboard extensions to the bridge, allowing improved side and rear sightlines, often installed with duplicate controls used for berthing and close manoeuvres.


A loop of line that evenly distributes the pull on a towline.


Twin masted all square rig sailing vessel.

A ships goal.


Twin masted sailing vessel, all square rig on the foremast and all fore and aft rigged on the aft mast.



A term used to describe wood that is finished natural, using varnish or other clear coating.


To slew round on a wave front.

Broach reach:

Any point of sailing between a beam reach and a quartering wind.

Broad axe:

Shipwrights axe used to initially smooth a face on timber.


A seam in a sail, in which the edges of neighbouring panels are cut in a convex curve, so that when sewn together the panels force fullness into the sail.


Bunkers remaining on board.

Broken stowage:

Volume of unoccupied space in a loaded ship due to the irregular shape of the cargo and consequent spaces between.

Broken water:

Turbulent and rough sea.


An agent who facilitates a contract for a fee.


Small stream.

Brook trout:

Salmon related fish, Newfoundland.


To bring a vessel to a stop.


A plate to shed away from an open port, also called a watershed.

Brow gear:

A gangway from ship to shore and its accessories.

Brown trout:

A common trout, European.

Bruce anchor:

One piece designer anchor with three clawed crown.

Buckled plate:

A warped plate or one that is wider at the centre than at the end.

Brush box:

Tall Australian hardwood used principally for flooring timber.



Carbon contacts projecting from a sleeve and brought to bear by spring pressure on the commutator of an electrical generator.


Originally a term for English sea rovers that preyed on Spanish merchantmen in the West Indies. Name thought to be derived from their dried blood coloured red pantaloons – boufe canires or meat eaters- it is now commonly used to describe any pirate.

Building slip:

An inclined berth where ships are built.

Bulbous bow:

Bows constructed with a bulb shaped projection rising from the bottom.

Bulbous forefoot:

A convex entry at the keel/stem junction (as opposed to a sharp vee) incorporated to soften the ride. When used in conjunction with a reverse curve at the chine, it usually makes sheet materials impractical requiring other planking methods in the forward section.

Bulldog clip:

A threaded u bolt that will tenaciously grip two steel wire ropes due to its shaped clamping saddle tightening around the wires. To temporarily replace an eye splice, four clips should be used separated by a distance of 8 times the diameter of the wire.


A hawser used to prevent a ship’s bow from bumping against its mooring buoy.

Bulk cargo:

Unpackaged cargos, e.g. coal, ore, grain.

Bulk carrier:


Ship designed to carry unpackaged (flowing) dry cargos such as grain, sand, cement, ores, coal, etc.


Partitions to reduce water or fire engulfing all parts of the vessel in the case of accident.

Bulkhead stiffeners:

Reinforcing steel sections along a bulkhead, most commonly vertical but horizontal (or a combination) may be used.

Bull nosed bow:

A large and rounded underwater bow profile designed to displace water and reduce overall drag..

Bull riveting:

High powered air or hydraulically driven rivets.


Walling around a vessel above deck, fastened to stanchions.

Bulwark stay:

A brace between the deck and bulwark to increase its rigidity.


A ship to shore boat used for reprovisioning. (derived from boom boat)


A spar at the stern to carry a backstay.


The assembling of pieces of cargo into manageable units, in practice, of the weight of the available fork lift truck’s capacity.


Conical shaped timber or cork to seal a hole in the vessels skin.




Fuel consumed or compartment where solid fuel (coal) is stored.


The middle of a sail.


Material from which flags are made.

Flying flags for celebration. (Dressing ship with bunting)


A floating marker, secured to the seabed, used to indicate danger or other to assist mariners.


The upthrust upon a body that is partially or wholly immersed in a liquid. Colloquially, the ability of an object to float.

Buoyant lights:

An automatically activated light (2 hour’s duration) that can be deployed to assist in the search for a MOB at night.


Weight of cargo to load displacement.

Burdened vessel:

The boat not having the right of way.

Bureau veritas:

French ship classification society.


A small flag, either pointed or swallow-tailed.

Burr edge:

The rough edge of a metal plate.


Historic North Sea fishing boat.

Buss bar:

A heavy duty bar or strap used for making multiple electrical components connections onto one power line.


See LPG.


The end of a plank where it unites with the end of another.

Butt blocks:

Internal timber covering plates placed behind butts in the planking to reinforce that weaker spot.


A washing process to clean tanks using hot water/chemicals sprayed through a patented rotating nozzle.

Butterworth opening:

A deck access designed for butterworth gear.

Butt joint:

Components squarely joined together along their edges.

Butt strap:

A plate used to fasten objects together with their edges butted.


Designer’s lines derived from drafted slices drawn parallel to the centreline of a ships waterline plan and transposed to its profile plan.


A round deck item used to thread cables between vessels when they are laid together.

By the:

By the head.  When the bow is lower in the water than her stern.

By the stern.  When the stern is lower in the water than her bow.

By the board. Over the side.

By the run.     To let go altogether.

By the wind.   Close-hauled.


A pipe controlled by a valve to re-route a fluid around a flow system.

Back to top



Code flag;        Affirmative.

Sound signal;   Affirmative.

C flag + three numerals:

Code flags;   Course.


Coarse Acquisition - the radio signal on the L band frequency of 1575.42 MHz that civilian GPS receivers use. As opposed to the P code used by the US military.


A shelter at the corner of a bridge.


The living accommodation on a vessel.

Cabin sole:

The decking of the cabin that you walk on.



A unit of measure being one tenth of a nautical mile.

A strong line or chain by which a vessel is secured to its anchor.

Cable clamp:

See bulldog clip.


Rope (usually) left-handed of nine strands, in the form of three three-stranded, right-handed ropes.

Cable locker:

A forward compartment on small craft used to store the anchor cable.

Cable ship:


Ship constructed for laying and repairing telegraph and telephone cables across oceans.


Coasting trade. Reservation of such trade to flag nationals.


A young maritime worker trainee.

Class of 11 foot sailing dinghy.


See classical winds.


A mound of stones often built as a memorial or conspicuous mark.


A structure used to close off the entrance to a dry-dock.

Calculated altitude:

Angular height of a celestial body above the horizon calculated as opposed to worked from sight reduction tables.

California current:

A cool North Pacific Ocean current setting Southerly along the North American Western coastline.


A dusty wind off the Sahara that blows over the Canary Islands in winter.


See caulk.

Call sign:

A ship’s unique identifying code.


An elliptical protrusion along a shaft that on each revolution displaces a following lever (cam lifters).


See Beaufort scale.


Roundness of deck that sheds water.

Fullness of sail created by sail maker; also called draught.  It can be altered by bending the mast’s middle forwards and bending the boom downwards.

Cam cleat:

Sprung loaded mechanism whose jaws will jam a rope under strain.


A tank that is sunk and attached to a wreck, subsequently being filled with air to refloat it.

A decked vessel with high stability for use in lifting sunken structures.

A wooden float between a vessel and a dock used as a fender.

Cam shaft:

A shaft with a row of eccentric sections for opening and closing the valves of a motor.


A dug or dredged waterway.

Canaries current:

A cool North Atlantic current setting southerly along the North African Western coastline.


A unit measure of luminous intensity based on a comparison with a candles brightness (candle power).


Narrow, light, low freeboard vessel propelled by paddles.


At an angle. Consequently:

Cant beam- beams supporting the deck plating or planking in the overhanging part of the stern of a vessel.

Cant body- where the planes of a vessel’s frames are not at right angles to its centreline.

Cant frame- Hull side frame not perpendicular to the vessel’s centreline.

Canute, King:

11th century British king who is said to have demonstrated the limits of a king’s powers by ordering the incoming tide to retreat to no avail.


Heavy duty woven material used for sails and tarpaulins.


A technique of covering timber or ply with painted canvas to waterproof a deck etc.


A deep gorge or ravine with steep sides.


The ironwork that attaches a mast with its topmast.


A temporary electrical storage device that blocks DC flow while allowing AC oscillations.

Capacity plan:

Plan of vessel showing capacities of all holds, tanks and other relevant compartments.


A headland projecting out to see beyond the adjacent coastline.


A small bait fish, N. Atlantic, also called caplin.


A large cargo vessel that cannot transit either the Panama or Suez Canals, typically greater than 120 000-180 000 DWT.

Cap shroud:

Supporting wires from either side of a mast leading over spreaders to support its upper sections.


To overturn.


A winch with a vertical rotating drum, used for handling mooring ropes and wires.


A wooden bar used to manually turn the capstan.


Master of a ship or pilot-in-command of an aircraft, commanding officer of a warship or an operator of any other vessel.


Historic lateen rigged Mediterranean merchant ship capable of windward performance.

Carbon ceramic seal:

A pump seal consisting of a sprung carbon shaft ring closing onto a ceramic pump body seat.

Carbon dioxide:

A natural atmospheric gas (CO2) that is increasing due to man’s activities and contributing to the greenhouse effect.

Carbon monoxide:

A deadly product of combustion (CO).

Car carrier:

Special purpose vessel for transporting cars.

Car deck:

A deck on which cars are carried.

Cardinal points:

The four primary compass directions.


To heave a vessel down on her side for repairs.


Trade goods and freight carried by a vessel.

Cargo battens:

Strips of wood used to keep cargo away from the hull plating.

Cargo cult:

Worshippers of articles brought to remote lands as trade goods.

Cargo door or port:

Watertight door in the hull side through which cargo is loaded or discharged.

Cargo handling:

The act of loading and discharging a cargo ship.

Cargo manifest:

A list of all cargo carried on a specific vessel voyage.

Cargo net:

A net for securing cargo during loading/unloading.

Cargo plan:

Determines and describes the stability, stowage, segregation, precautions and quantity of the goods carried after loading is completed.

Cargo preference:

Reserving a portion of a nation's imports and exports to national-flag vessels.

Cargo register:

See Cargo manifest.

Cargo sweat:

Condensation formed on cargo when transported from cold climates to warm.

Carlins, carlings:

Support timbers running between the decks beams around hatch openings.

Carpenters trunk:

Access to side lights cabinet.


Historic large Portuguese sailing merchantman with fortified stern castle.

Carrick bend:

A decorative knot.


Owners or operators of vessels providing transportation to shippers. The term is also used to refer to the vessels.

Abbreviation of aircraft carrier.

Carry away:

To break or loose a component due to stress of weather.

Carry on:

To proceed.


Local cargo haulage by drays or trucks (also called drayage).


Map and chart making.


Edge to edge planking that creates a smooth surface, unlike clinker construction.


Centreboard case.

Case dogs/hooks:

Pair of spiked clamps fitted to crates to facilitate lifting.


A lining built around the ship’s funnel to protect the decks from heat. See Air Casing.


To throw.

To begin.


An artefact produced by pouring molten metal into a mould.

Cast off:

To let go the lines that secure a vessel to a berth.


A twin hull vessel.


An agent that provokes a reaction.

Chemical added to polyester/epoxy resins to assist curing.

Cat boat:

A sailboat with one mast, well forward, without headsails.


The nobler metal of an electrolytic cell. See anode.

Cathode protection:

Sacrificial or impressed current system of corrosion protection used on vessels.

Cat o’nine tails:

An instrument of punishment being a whip with nine strands as the terminal.

Cat’s paw:

A hitch made in a rope.

A light current of air on the surface of the water.

Cattle carrier:

Ship built to carry cattle.


A rigid catamaran tug connected to a barge. When joined together, they form and look like a single hull of a ship; ocean-going integrated tug-barge vessels.


A raised fore and aft walkway affording safe passage over the pipelines, deck obstructions and wet decks.


A portion of amniotic sac that can stick to a baby’s head during birth. In the past superstitious mariners believed it provided lifelong immunity from drowning, but was also traded as a protective totem for any owner.


Filling the seams of a vessels planking with oakum or cotton.

Caulking iron:

Flat edged tool used to drive caulking between plank seams.

Caulking mallet:

Wooden hammer used with a caulking iron.


A raised pathway across swamp or water.

Caval (kevel):

A two armed metal deck fitting around which a vessel’s lines are made fast.


Reduction in propeller efficiency caused by air pulled down around its blades.


Sand or coral islet.


A vessel constrained by its draft.

C. Class:

Australian vessel survey class, 30NM offshore.


Compass course to steer.


Close circuit television.


Chart datum.


An inside plank sheathing of a vessel that covers the frames and enables easy cleaning of the hold spaces.

Celery top:

Australian timber prized for planking.

Celestial navigation:

To position find by observing the stars.


An anode and a cathode immersed in an electrolyte create a potential difference.  This cell is a source of electrical current responsible for corrosion. The anode and cathode may be separate metals or dissimilar areas on the same metal.  Also called an electrolytic cell.


Compartments of a container ship into which containers fit.

Cellular container ship:

A container vessel with vertical cell guides for standard sized containers limiting movement and lashing requirements.


Celsius temperature scale:

Temperature scale of 0º (freezing water) to 100º (boiling water).

Celsius = (Fahrenheit - 32) x 5/9.


A plate that can be lowered to reduce a sailing boat’s tendency to make leeway when on the wind.

Centreboard case:

A watertight box that houses the centreboard.

Centre castle:

Raised part of a vessels hull amidships.

Centre of buoyancy (B):

The centre of area of the underwater transverse or longitudinal section of a hull at a particular trim, hence the point at which the force of buoyancy is regarded to be acting vertically upwards

Centre of effort (CE):

The centre of areas of all sails or areas of a waterline.

Centre of flotation (F).

This is the centre of gravity of the area, or centroid, of the water-plane of a ship and is equivalent to a pivot point of the vessel on any change of trim.

Centre of gravity (G):

The centre of weight of a vessel, hence the point at which the force of weight is regarded to be acting vertically downwards.

Centre of lateral resistance (CLR):

The centre of area of the designed underwater longitudinal profile of a hull around which a vessel will pivot from wind on the beam.

Centrifugal action:

The process of dragging gas or liquids through the central inlet of a revolving turbine and flinging it out at its circumference at increased velocity.

Centrifugal pump :

A rotary, usually solid bladed pump that sucks from its centre and exhausts from a point on the circumference of the rotor’s housing. They are not self priming.


A dry northerly wind of the Gulf of Lyon, southwest France.

Certificate of operation:

A document specifying the operational conditions of an Australian domestic commercial vessel.

Certificate of registry:

A document that specifies the national registration of the vessel.

Certificate of survey:

A document specifying the survey details of an Australian domestic commercial vessel.


A marine mammal including whales and dolphins.


Chlorofluorocarbons (traditionally used in refrigerants and fire extinguishers) are chemicals that diminish the ozone layer.


Wear on the surface.  Chafing-gear is wrapped on rigging and spars as prevention.

Chain locker:

Locker for stowing anchor chain.

Chain plates:

Metal plates bolted to the side of a vessel, by which the lower rigging is secured to the hull.

Chain riveting:

Paired rows of rivets spaced adjacently.


Anchor chain.

The extremity of the channels on sailing ship.


To take off the edge, or bevel the plank.


A supplier of ships stores.


A naturally deep or dredged route through a shoal area.


Extension boarding at deck level to increase the width of the hull of a sailing ship for the lower stays land upon, thus providing a wider angle of mast support. The traditional position from which a seaman heaved a hand lead line (to establish depth).


See sea shanties.

Charley noble:

A galley’s stove pipe.


An image of geographical place that shows positions and navigational features.

Chart datum:

The level below which soundings are given and above which drying heights are given on charts.


To hire a ship.

Chart house or room:

A compartment adjacent to the bridge for charts and navigation.

Charter party:

A contract between ship owner and a cargo owner, usually arranged by a broker, where a ship is chartered either for a voyage or a period of time.


A deep fissure in the earth’s surface.


The backbone frame of a vehicle or a machine.

A wheeled frame that fits to a container enabling it to be moved.


To temporarily restrain a line, as to check to cable from paying out.

Check (in wood):

Longitudinal separation of the fibres in wood that do not go through the whole cross section. Checks result from tension stresses during the drying process.

Checksum digit:

A digit that is appended to a numeric data element and used to verify its accuracy. Checksum digits are computed by adding the digits of the data element.

Check valve:

A one way valve.

Cheeks plates:

The sides of a block that retain the pulley sheaves.


A bundle of spun yarn.

To spread out a rope or twine.

Chemical carrier:

A vessel purpose built to carry of volatile, poisonous or corrosive liquids.

Chief or chief engineer:

The senior engineer officer responsible for the satisfactory working and upkeep of the main and auxiliary machinery aboard ship.

Chief mate:

The deck officer second in command of a ship. He assumes the position of the Master in his absence.


A greasy pencil.


The join between the bilge and topsides of a hull.

Double chine - Having an additional planking junction between the chine and the sheer, giving the hull a more rounded look.

Hard chine- Having a distinct bottom/side planking junction as opposed to a rounded curve.

Multi-chine - Having one or more additional planking junctions between the chine and the sheer.

Chine log:

Longitudinal member used to reinforce the join of sides and bottom of flat or V-bottom hulls.


A dry snow melting katabatic wind of the American Pacific North.


Chemicals releasing chlorine atoms that destroy the ozone layer.

Chock boat:

A support for a lifeboat.


Wedges used to secure anything with, or to rest upon.  The long boat rests upon two chocks, when it is stowed.

A fillet of wood used to make good a deficiency in a plank.




When the lower block of a tackle is pulled so tight to the upper one, so that it will hoist no higher; also called two-blocks.


A mechanism to provide richer mix while starting a petrol engine.

An electrical coil to block out radio interference (noise).


The tackle falls jammed within a block.


A straight line between the luff and leech of a sail.

Chosen position:

A chosen Lat. and Long. Within ½ degree of a vessels position to facilitate a celestial navigational fix.


Accurate ship’s timepiece (clock).


A sprung split ring that fits onto a groove of a shaft and thus retains other shaft fittings from falling off the otherwise open end.

Circuit breakers:

A safety device used in electrical systems to cut the supply of electricity when a fault is evident.

Cirrus clouds:

The highest, feathery, ice clouds.

Civil twilight:

The time between sunrise/sunset and when the suns position is at 6º below the horizon.



Longitudinal timbers connected to the frames to support beam ends.

Class 1 vessel:

Passenger            (NSCV vessel survey category)

Class 2 vessel:


Class 3 vessel:

Fishing vessel

Class 4 vessel:

Hire & drive vessel

Class A vessel:

Unlimited offshore

Class B vessel:

200NM offshore

Class C vessel:

30NM offshore

Class D vessel:

Partially smooth waters

Class E vessel:

Smooth waters

Classical winds of the ancient world:

The winds and their points (direction) of the ancient world are translated the Vatican’s 2nd century engraved stone table of winds, approximated as below:


  Point                  Roman                    Greek


N                        Septentrio               Apartias

NNE                   Aquilo                     Boreas

NE                     Vulturnus                Caecias

E                        Solanus                  Apheliotes

SE                      Eurus                      Eurus

SSE                    Euroauster              Euronotos

S                        Auster                      Notos

SSW                  Austroafricus            Libonotos

SW                     Africus                     Lips

W                       Favonius                  Zephyrus

NW                    Corus                       Argestes

NNW                  Circius                     Thrascias

Classification societies:

International organizations that monitor and certificate standards of construction, repair and survey of vessels – operators’ compliance is rewarded with ease of access to foreign ports, cheaper insurance rates and higher vessel resale value. Class societies include:

American Bureau of Shipping -America

Bureau Veritas-France

Det Norske Veritas-Norway

Germanischer Lloyd-Germany

Lloyds Register of Shipping-UK

Nippon Kaiji Kyokai-Japan

Clawing off:

To sail off close-hauled from lee shore.

Clean ships:

Tankers whose cargo tanks are free of traces of impurities that remain after carrying crude or heavy fuel oils.






A vessel clears before sailing from a port when documentation is lodged at a Customs House.

Rigging are cleared when tangled gear is untangled.

Land is cleared when left when a vessel sails beyond coastal dangers.

The bilge is cleared when pumped dry.

Clear away:

To remove restraints from gear in preparation to anchor.

Clear berth:

The circle that is available for a ship to swing clear of obstructions within its anchorage. Opposite of foul berth.

Clearing marks:

Natural or constructed navigational marks in transit that when sighted open of each other mark a track clear of dangers.

Clearing line:

Transit that clears charted navigational hazards.


A fitting for used to secure a line.


Tying a rope to a cleat.


To bend over the internal end of a copper nail after it has been driven through the plank, thus increasing its holding power.

Clevis pin:

A headed rod with holed end to accept a split pin, used as a shackle bolt or similar.


The corner of a sail between the leech and foot.

Lower after sail corner.

Clew lines:

The two brails that lead to the clews of a square sail.

Clewed up:

Anchor back at the ships side on retrieval.


A tackle to stretch the foot of a sail along the boom.


The mean of weather conditions.



Lapstrake planking, where planks overlap their edges, as opposed to carvel (smooth planking).


A fast, highly canvassed, fully rigged ship.

Clipper bow:

A bow where the stem has a forward curve and sides have a lot of flair. Also called a schooner bow.


To approach.


When a vessel is sailing into the wind.


When the sails are fully reefed.


Ice, water and vapour visible in the sky.

Cloud cover:

The proportion of the sky covered by visible cloud measured in units of Octas, from one (minimal cover) to eight (full cover).


Two half-hitches around a spar or rope; suitable for objects not under strain.

Club foot:

The flat, broad after end of a vessel’s stern foot section.

Club foot jib:

A jib with a boom or "club" on the foot of the sail.


A mechanism to couple or uncouple a drive shaft from its engine.


Radar echoes from waves or precipitation, occurring randomly in the display which may obscure echoes from small targets.


Course made good.


Compressed natural gas.


Contract of Affreightment -  in which (typically) an owner agrees a price per revenue ton for cargo on a specified  voyages.

Coach bolt:

A bolt with a round head above a squared section of shank that pulls into the timber and resists turning as the nut is tightened.

Coach roof:

A section of the cabin constructed above deck level.

Coach screw:

A screw with a hex or square head (lag bolt).


Vertical structures to stop water entering, as around a cockpit.

Coastal plain:

Low lying land along the edge of the coastline.

Coastal waters:

Sea area along the edge of the coastline.

Coast earth station (C.E.S.):

Maritime name for an Inmarsat shore-based station linking ship earth stations with terrestrial communications networks.


A piece of canvas, tarred or painted, placed around mast or bowsprit where it enters the deck, to keep out water.

Coastal radio:

Radio traffic in inshore waters


Coastal operating vessel.


Navigating form headland to headland.

Coaxial cable:

An insulated conducting cable surrounded by an insulated conducting sleeve used for connecting an aerial to its transceiver.


Sea worn rounded rocks or pebbles.

A small open type of rowing boat.


A valve.


An anchor hanging by the ship's side.

Cocked hat:

The gap between the intersections of three imprecise position lines when plotting on a chart.


A deck area that is lower than the sheer line of the boat and exposed to the elements.


A large marine fish.

Cash on delivery.

Code flags (letters):

Alphabet of flag signals for speaking at sea, as included at each letter heading in this dictionary.

Code flags (numerals):












Sub 1

Sub 2

Sub 3

Coefficient A:

That part of a vessel’s magnetic deviation that is constant on all headings, +A for Easterly and -A for Westerly. See apparent coefficient A.

Coefficient B:

That part of a vessel’s magnetic deviation (caused by permanent or induced magnetism) that varies as the sine of the compass course, contributing to maximum deviation when heading East or West, and minimum deviation when heading North or South.

Coefficient C:

That part of a vessel’s magnetic deviation (caused by permanent or induced magnetism) that varies as the cosine of the compass course, contributing to maximum deviation when heading North or South, and minimum deviation when heading East or West.

Coefficient D:

That part of a vessel’s magnetic deviation that varies as the sine of twice the compass course, contributing to maximum deviation when heading NE, SE, SW and NW and zero deviation when heading N, E, S or W.

Coefficient E:

That part of a vessel’s magnetic deviation that varies as the cosine of twice the compass course, contributing to maximum deviation when heading N, E, S or W and zero deviation when heading NE, SE, SW and NW.

Coefficients of fineness:

Used to describe the underwater form and hull shape, being ratios of areas and volumes to their circumscribing rectangles or prisms.

Coefficients of form:

Used to describe the shape of the ship's hull when comparing one with another. The coefficients are used in power, stability, strength and design calculations.

Coffer dam:

The void space between two bulkheads is called a cofferdam.

Coffin plate:

An inverted boss plate.


Course over ground.


To lay a rope up in a circle, with one turn or fake over another.  A coil is a quantity of rope laid up in this manner.


Meteorological term for area between high and low pressure systems.

Cold bent frames:

The internal frames of a vessel that are made curved without the use of heat, often possible by using fresh unseasoned timber of a pliable nature.

Cold cranking amps:

The amps delivered by a lead acid battery over 30 seconds while maintaining at least 1.2 volts per cell at 0º F (approx -18ºC).

Cold front:

The boundary where a parcel of cold dense polar air (advancing towards the equator) drives underneath the warmer air ahead.

Cold moulded:

Timber construction process that uses several layers of thin strips of timber stapled over a former. Each complete layer is separated from the other by a waterproof membrane.

Cold plug:


A spark plug with low insulator seat which quickly carries the heat from the core, designed for high-speed operation.


A ring of plate positioned around a pipe or mast at a bulkhead or deck opening that serves to provide a sealing reinforcement.


A split circular inset that tightens on a shaft when longitudinal compression is applied, used in winch clutch or drill chuck applications.


A vessel employed in carrying coals.

Collision bulkhead:

First watertight bulkhead abaft the bow.

Collision mats:

Canvas mats constructed as a emergency cover for any hull damage, where the hull may have been punctured.

Collision regulations:

An IMO Convention, The International Regulations for Preventing Collisions at Sea.

Columbus, Christopher:

Commonly attributed as the first European discoverer of the West Indies (New World), believing it the west extremity of the Far East (the Indies) by virtue of miscalculating the globe’s circumference. Subsequent revelations point to earlier visitations to the American continent.


Identity of a vessel (as shown by flying the national flag).


A derrick head.


Step long swell with high and breaking crests.


Combination passenger/cargo vessel specifically designed for containers and conventional cargoes.


A raised edge around any opening that helps prevent water entering.


This process occurs when trapped air is compressed and heated in the cylinder igniting fuel which is injected into the cylinder.


After hauling a rope, to come up is to hand the rope forward so it can be made fast.

Coming about, coming around:

To put a sailing vessel into the wind and tack.

Commercial purpose:

For the purposes of NSCV Part B, use in connection with a commercial transaction of any kind including operations as a business, as a service (including a service provided by the Crown), for profit or for research.


An apprentice waiter.

Common ground point:

A junction point used to establish earth for an electrical system.


The rotating cylinder of copper contact segments attached to one end of the armature windings of a generator.


A wooden covering over the staircase to a cabin.

A companion-way; staircase to the cabin.

A companion ladder; leading between decks.


A space or room in a ship.


An instrument that indicates direction.

A magnetic compass has a  pointer that is attracted towards the Earth’s magnetic north.

Compass timber:

Structural timbers sawn from the bows of trees so the grain follows the shape, thus providing great strength.


The number of persons on a vessel.

Composite construction:

The use of a mix of materials for a hull’s construction.

Composite group flashing:

Flashing navigational mark of a combination of alternating groups of differing numbers of flashes.

Composite group occulting:

Occulting navigational mark of a combination of alternating groups of differing numbers of occultation.


The pressure generated in the engine cylinder as the piston rises forcing trapped air to the top of the cylinder.

Compression ratio:

The ratio of the piston’s swept volume and that remaining unswept of the cylinder - typically 10:1 plus in petrol and 16:1 plus in diesel high speed combustion engines.


A pump to compress refrigeration gasses.

A lever in 18th century sail fighting ships that brakes the anchor cables by squeezing.


Committee of Radio Communications and Search and Rescue.


A arrangement where a private party (concessionaire) leases assets from a public entity to enjoy contractual investment and termed revenue rights that revert to the public on the contract term expiry.

Conclusion stage:

A period during a SAR incident when SAR facilities return to their regular location and prepare for another mission.


To change from a gas to a liquid.


A storage device for direct current connected across the breaker points. It is used to minimize arcing at the points, and its discharge boosts the voltage in the secondary circuit for a hotter spark at the plug.

A device that cools refrigerant gas giving up heat to the surrounding fresh air and returning the refrigerant to liquid state.


The moving of heat through solid material.


An electrical conductor is a material which will carry electric current. Most metals, sea-water, the earth, and your body are all conductors. The term is often used for a wire in an electric circuit. Wire conductors must be large enough to carry the circuit current without overheating.


A pipe for cables.

Confined space

A tank or void space that is not normally a workspace that is poorly ventilated and may contain an atmosphere that will not sustain life.


The join of two streams or bodies of water.


Directing a helmsman in steering a vessel.

Conning tower:

The raised surface operating control station of a submarine.

A protective armour plated control station.

Conrad, Joseph:

Seaman, master and author of colourful sea stories from the days when sail was giving way to those of steam.


Goods placed with a carrier for delivery to a consignee.


Person to whom carried goods are to be delivered.


Person who places goods with the carrier to be delivered to the consignee.

Conspicuous object:

Readily identifiable mark useful for navigation.

Constrained by her draught:

A power-driven vessel which because of her draught in relation to the available depth and width of navigable water is severely restricted in her ability to deviate from the course she is following.


A box used to transport cargos from door to door without handling the contents. Standard sizes of these metal containers are 20ft or 40ft by 8ft wide and 8.5ft high.

Container terminal:

Purpose built port facilities for loading, unloading storage and stowage of cargoes in containers.

Container ship:

A vessel designed to carry standard containers.


Occurs when foreign materials or impurities enter the fuel, oil or water.


One of the six main continuous bodies of land on the planet.

Continental shelf:

Zone of shallow water adjacent to the continent whose seaward extremity quickly drops away to greater depth. Usually regarded as the 200mtr sounding line, but in local terminologies may mean from 100mtrs to 350mtrs.


The completeness of an electrical pathway.


Cargo that is prohibited.

Contract of affreightment:

A service contract under which a ship owner agrees to transport a specified quantity of products at a specified rate per ton. This contract differs from a spot or consecutive voyage charter in that no particular vessel is specified.


Lines joining equal depths or heights.


The moving of heat through liquid or gas by currents; a process commonly associated with warm rising air.


The meeting boundary of two differing currents or winds.


A number a vessels steaming in concert.

Cook, Captain James:

18th century explorer and cartographer, recognised as leader of the first expedition to chart the East Coast of Australia.

Cooling water:

Circulated water that removes the heat from an internal combustion engine.

Circulated water that removes the heat of compressing and condensing the refrigerant in refrigeration systems.


The bringing together of organisations and elements to ensure effective search and rescue response. One SAR authority must always have Overall coordination responsibility and other organisations are to cooperate with this agency to produce the best response possible within available resources.

Coordinated search Pattern:

Multi-unit pattern using vessel(s) and aircraft.


Coordinated universal time (U.T.C.):

International term for time at the prime meridian.



Hard calcareous matter produced by marine polyps that forms underwater reefs.

Coral bleaching:

Die back of corals caused by excessive water temperatures.


Is used to denote fibre ropes only.


A mountain province.


The central filament in a wire rope.

Coriolis Force:

The apparent force, caused by the earth’s rotation, which Force deflects moving air (and water to a lesser extent) to the left in the Southern Hemisphere and to the right in the Northern hemisphere.


The decay of a metal or alloy by chemical or electro-chemical reaction with its environment.


Materials having an undulating shaped profile of grooves arranged to increase stiffness of steel sheeting.

Corrugated bulkhead:

Bulkheads having an undulating shaped profile of grooves arranged to increase stiffness.


Historically a North African pirate or privateer.


Historically a fine lined French twin masted square rigged vessel or a British flush single gun deck warship.

Now a fast naval escort vessel.

Cospas-Sarsat System:

Russian - American satellite system designed to detect distress beacons transmitting on the frequencies 121.5 MHz, 243 MHz and 406 MHz.

Cotter pin:

A split pin. After slipping through the hole of a clevis, its arms are prized open to prevent its withdrawal.


The overhanging after section of the stern.

Countersunk hole:

An edge bevelled hole in a plate allowing a matching tapered bolt head to seat flush with the plate’s surface.

Countersunk rivet:

A rivet head seated flush with the plate surface


Two or more dissimilar metals or alloys in electrical contact with each other that act as the electrodes of an electrolytic cell if immersed in an electrolyte.


The link between two parts of a shaft or shaft & drive system.


The intended direction of travel of a vessel.

The direction that a vessel is steered.

Course made good:

The track that was achieved over the sea bed (ground).

Course sail:

The lowest and largest square sail set on the masts of a sailing ship.


A radar display in which the picture is compass-stabilised so that the vessel’s intended course is straight up the screen.

Couta boat:

Traditionally a beamy open fishing boat of Australian design, now favoured by enthusiasts as a recreational sailing dinghy.


A small cliff bound bay.

Slang for a person.

Cove line:

A decorative incision along the sheer of a vessel often picked out in gold or another contrasting colour.


The hood shaped cap of a ventilator.


The man in charge of a boat.

Australian certificate of competency to master a vessel of less than 12 metres in measured length.

Coverage factor (C):

For parallel sweep searches, (C) is computed as the ratio of sweep width (W) to track spacing (S).          C = W/S.

Covering boards:

The boards at the edge of the deck that cover the frames and planking at the join of the hull and deck of a vessel.


In radar plotting the closest point of approach of a target in miles.


Cardio pulmonary resuscitation.

C.Q.R. anchor:

Also called a plough anchor due to its shape and action.


To catch a crab is to feather the oar in the water too soon, resulting in no forward thrust.


Sideways movement, like a crab.


A frame to support a hull ashore.


Any air, sea-surface or submersible transporter.


See below.


A vessel that is easily heeled or listed.


The central magma outlet tube of a volcano.

A ground depression caused by explosion, impact or remnant from extinct volcano.

A depression in a weld as the result of molten metal displaced from the weld point.


A lobster.


Tiny cracks which appear in the outer surface of varnish, paint or gel coat.


Top of a wave.

The maximum positive amplitude of a radio wave.


The people manning a ship.

Crew’s gangway:

A walkway elevated over the deck for crew’s safe passage across awash decks in stormy weather.


The foundation of heavy blocks that support  a vessel during construction.


To recruit a crew by trickery or hijack.

Crimp terminal/connecter:

Light duty compressible fittings used to join low voltage DC circuitry. Available in spade or barrel type male to female configurations.


A rope eye worked into edge or clew of a sail, reinforced by a thimble.


A Dutch 16th century shoal water fighting ketch.

Cross curves of stability:

Graphical curves of  a ship’s transverse stability for ranges of heel angle and displacement.


A mechanism in large reciprocating engines that constrains the piston, rod and bearing, so eliminating sideways pressure on the assembly.


A pipeline that crosses over a mechanism or space providing flow from a source to a destination.

Crossing the line:

Crossing the Equator; traditionally the occasion of a celebration where a pantomime King Neptune and his court challenge first time initiates leading to punishments and rewards.


The lowest square sail set on the mizzen of some sailing ships.


Plank laid in a transverse fashion, usually along the bottom of a chine built hull.

Cross sea:

Waves running contrary to and on top of the prevailing swell.


A temporary horizontal brace to hold a frame in position, ultimately replaced by deck beams.


Spreader fixed to the mast to anchor the shrouds.


The bottom (terminal) part of an anchor on which the flukes are attached.

The camber of a deck.

Crow’s nest:

A viewing platform at the mast top.


Cathode ray tube.


Historically a privateer.

A large lightly armoured warship with medium sized guns, used for commerce protection and scouting.

Cruising guide:

Navigational booklet describing a limited area in detail.


A hard shelled (usually) aquatic animal; the crab, lobster etc.


Support for a boom.


Course steered.


A marine animal with comb like teeth or scales.


Course to steer.


A small cabin.


A tunnelled drain.

Cumulonimbus cloud:

Heavy, dark cloud of great vertical depth often with an anvil shaped head, bringing rain.

Cumulus cloud:

Woolly medium height clouds.

Cunningham eye:

Eye in a sail’s luff near the foot through which a line is passed to increase luff tension and flatten the sail.


A directional movement of water.


An electronically-generated cross hair used to indicate a position on a raster scan display.


A sagging line caused by a too much paint or varnish on a vertical surface.

Custom broker:

An agent accredited by a customs authority to manage compliance for an importer.


A customs office where duties on imports are settled.

Customs and excise:

A government agency tasked with collecting and enforcing taxes on dutiable goods, particularly imports and exports.


A single-masted sailboat with multiple-head rig.


An angled change in the underwater longitudinal profile of a vessel between the bow and keel or between the stern and keel. Sometimes called cut up.

Cutlass bearing

A ribbed rubber insert within a metal tube that allows water lubrication of an outer propeller shaft bearing.


The foremost part of a vessel’s stem.

C.V joint:

A constant velocity joint. It allows considerable misalignment within a drive train.


A repeating or rotary phenomena.

Cycloidal propulsion system:

The Voith Schneider propeller or tractor system using adjustable vertical hydrofoil blades, independently rotating on a circular base mounting that by developing lift can direct propulsion in any direction.


The rapid development/intensification of a low pressure system.


An intense tropical revolving storm in the Southern Hemisphere, also called hurricane or typhoon in the Northern Hemisphere.

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Code flag;         Keep clear of me, I am manoeuvring with difficulty.

Sound signal;    Vessel with manoeuvring limitations in restricted visibility.

D flag + six numerals:

Code flags;    Date

Dagger board:

A non-pivoting board slotted into a sailing boat’s keel to minimize leeway; it is raised and lowered through a watertight case and can be entirely removed.


Dry adiabatic lapse rate is approx. 9.8º C per kilometre being the temperature change of unsaturated air on rising or falling.


A bank built to contain a waterway.


Slightly wet.


Bread, risen (aerated) by bicarbonate of soda rather than yeast.

Dampier, William:

17th century British seaman, buccaneer, explorer, hydrographer and cartographer recognised as the first European explorer to land on the Western Australian Coast.


A torque applied to a gyroscope to assist it in settling in the meridian.

Danforth anchor:

A light duty stowable anchor with plate flukes that swivel.

Danger angle:

A maximum angle set on a sextant over which a vessel will be navigating too close to an obstruction. See HAS and VSA

Danger line:

A limiting dotted line marked around a charted hazard.

Date line:

A civil modification of the 180º East or West meridian marking the zone where the date on the globe changes from one day to the next.


A geographic point, line, or area used as a reference in search planning.

Datum area:

Area where it is estimated that the search object is most likely to be located.

Datum line:

A line, such as the distressed craft's intended track line or a line of bearing, which defines the centre of the area where it is estimated that the search object is most likely to be located.

Datum point:

A point, such as a reported or estimated position, at the centre of the area where it is estimated that the search object is most likely to be located.


Structure supporting sheaves or blocks that projects over a vessel’s side or stern, to hoist up boats.

Davy Jones’s locker:

Mythical undersea domain of the devil, Davy Jones, in which drowned seamen are confined.


Approximate time for first light. See Astronomical, civil and nautical twilight.


A sailing boat with limited accommodation for short passages.

Day mark:

USA term for buoyage topmark.

DC (direct current):

Direct current (D. C.) is a form of electricity often supplied by batteries. It is conducted in a constant direction (see polarity).

Daylight hours:

Between sunrise and sunset. See twilight.

Day shape:

Black shapes shown in daylight to indicate the nature of a vessels condition.