Page type: Glossary
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[A-Z] (341)


Towards the rear, or stern, of a boat. Also, the back end of an aircraft.

Aviation Maritime

Abandon ship verbal

A verbal order to leave the vessel immediately, usually in the face of some imminent overwhelming danger. It is an order issued by the Master or a delegated person in command. It is usually the last resort after all other mitigating actions have failed or become impossible, and destruction or loss of the ship is imminent. Usually preceded by transmitting an SOS signal if time allows, and customarily followed by a command to 'man the lifeboats' or life rafts.



Abreast of or at right angles to the fore and aft line of the vessel

Aviation Maritime

Able seamanAB

A merchant seaman qualified to perform all routine duties, or a junior rank in some navies. Also, able-bodied seaman or AB.



On or in a vessel, synonymous with "on board".

Aviation Maritime vessel



Above board

On or above the deck, in plain view, not hiding anything.




Account (online)

A website account identifies a sign in with a username and password. An account might be as basic as just to receive and manage email subscriptions or hold more detailed information to enable faster communications with other users.



afloat and unattached to in any way to the shore or seabed. It may also imply that a vessel is not anchored and not under control, therefore goes where the wind and current take her, (loose from moorings, or out of place). Also refers to any gear not fastened down or put away properly. It can also be used to mean "absent without leave".

Maritime navigation

Advance Provisioning AllowanceAPA

Monies paid to a bank account for the Captain of the yacht to provision on the charterer’s behalf. Key provisioning are fuel, food, drinks and port fees. The Captain is obligated to keep all receipts and balance the account for the charterer. At the end of the charter, the Captain provides a full account of expenditures, and any amounts not used will be refunded.


Aeronautical Information ServiceAIS

A service established in support of international civil aviation, whose objective is to ensure the flow of information necessary for the safety, regularity, and efficiency of international air navigation.

Aviation navigation communications


Towards the stern or rear of the vessel

Aviation Maritime


Resting on or touching the ground or bottom.

Maritime navigation

Air Traffic ControlATC

A service provided by ground-based air traffic controllers who direct aircraft on the ground and through controlled airspace that can provide advisory services to aircraft in non-controlled airspace. The primary purpose of ATC worldwide is to prevent collisions, organize and expedite the flow of air traffic, and provide information and other support for pilots.



An area of land set aside for the take-off, landing, and maintenance of aircraft.



The shape of a surface such as a wing, blade, turbine or rotor that generates lift from air passing over it.



A complex of runways and buildings for the take-off, landing, and maintenance of civil aircraft, with facilities for passengers.


Airport apron

The airport apron, ramp or tarmac is the area of an airport where aircraft are parked, unloaded or loaded, refuelled, or boarded.



The speed of an aircraft relative to the air.


Airworthiness Advisory CircularAAC



Above the ship's uppermost solid structure; overhead or high above.



By the side of a ship or pier.

Maritime navigation

AlphaA verbal

A in NATO phonetic alphabet

Aviation Maritime navigation communications alphabet


A sensitive aneroid barometer calibrated and graduated to measure altitudes by the decrease of atmospheric pressure with height, used in aircraft for finding distance above sea level, terrain, or some other reference point.


Anchor noun

An object designed to prevent or slow the drift of a ship, attached to the ship by a line or chain; typically a metal, hook-like object designed to grip the bottom under the body of water.

Maritime hardware

Anchor ball noun

Black shape hoisted in the forepart of a ship to show that the ship is anchored in a fairway.

Maritime navigation hardware communications

Anchor light noun

White light displayed by a ship at anchor.

Maritime navigation communications

anchorage verb

Port charge relating to a vessel moored at approved anchorage site in a harbour.


Anchorage noun

A suitable place for a ship to anchor, usually an area of a port or harbour.


Anchor's aweigh verbal

Said of an anchor when just clear of the bottom. Often misspelled as 'anchor's away'.

Maritime navigation

Angle of attackAOA

The acute angle between the oncoming air or relative wind and a reference line on the airplane or wing.



A category of commercially available underwater hull paints (also known as bottom paints). They are applied as the outer (outboard) layer to the hull of a ship or boat, to slow aquatic growth.


Area Approach Control CentreAACC


Astern, to go astern

Go backward, put the engine in reverse


Asylum Harbour

A harbour used to provide shelter from a storm.

Maritime navigation

Attitude indicatorAI

A flight instrument that informs the pilot of the aircraft orientation relative to Earth's horizon, and gives an immediate indication of the smallest orientation change. Formerly known as the gyro horizon or artificial horizon.

Aviation navigation

Automatic Identification SystemAIS

An automatic tracking system that uses transponders on ships and is used by vessel traffic services. AIS is intended to assist a vessel's watchstanding officers and allow maritime authorities to track and monitor vessel movements, supplying unique identification, position, course, and speed. AIS information supplements marine radar, which continues to be the primary method of collision avoidance for water transport

Maritime navigation communications


An angular measurement in a spherical coordinate system: the direction of a celestial object from the observer, expressed as the angular distance from the north or south point of the horizon to the point at which a vertical circle passing through the object intersects the horizon.

Aviation Maritime navigation

Azimuth circle

An instrument used to take bearings of celestial objects.

Maritime navigation

Azimuth compass

An instrument employed for ascertaining the position of the sun with respect to magnetic north. The azimuth of an object is its bearing from the observer measured as an angle clockwise from true north.

Maritime navigation

Back and fill

To use the advantage of the tide being with you when the wind is not.

Maritime navigation

Backstays noun

Long lines or cables, reaching from the rear of the vessel to the mast heads, used to support the mast.

Maritime hardware


Heavy material that is placed in the hold of a vessel to provide stability.

Aviation Maritime

Bank (sea floor)

A large area of elevated sea floor or seabed.


Bar (sea floor)

A large mass of sand or earth, formed by the surge of the sea. They are mostly found at the entrances of great rivers or havens, and often render navigation extremely dangerous, but confer tranquillity once inside. Also, sand bar.



Relating to or denoting a boat or ship hired without a crew; a boat that you charter and run yourself, without a crew.


Bareboat charter

A bareboat charter or demise charter is an arrangement for the chartering or hiring of a ship or boat, whereby no crew or provisions are included as part of the agreement; instead, the people who rent the vessel from the owner are responsible for taking care of such things.



The width of a ship at the widest point or a point alongside the ship at the mid-point of its length. Also, a transmitted radio, sonar or radar signal.


Bear down

Turn away from the wind, often with reference to a transit. Also, bear away.

Maritime navigation

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