a membranous, winglike or paddlelike organ attached to any of various parts of the body of fishes and certain other aquatic animals, used for propulsion, steering, or balancing.

Nautical .

a horizontal, often adjustable, winglike appendage to the underwater portion of a hull, as one for controlling the dive of a submarine or for damping the roll of a surface vessel.

fin keel.

Also called vertical stabilizer. Aeronautics . any of certain small, subsidiary structures on an aircraft, designed to increase directional stability.

any of a number of standing ridges on an ordinarily hot object, as a radiator, a cylinder of an internal-combustion engine, etc., intended to maximize heat transfer to the surrounding air by exposing a large surface area.

any part, as of a mechanism, resembling a fin.

Metallurgy . a ridge of metal squeezed through the opening between two rolls, dies, or halves of a mold in which a piece is being formed under pressure. Compare flash ( def. 11 ) .

Automotive . an ornamental structure resembling an aeronautical fin that is attached to the body of an automobile, as on each rear fender (tail fin).

Slang . the arm or hand.

Usually, fins. flipper ( def. 2 ) .

to cut off the fins from (a fish); carve or cut up, as a chub.

to provide or equip with a fin or fins.

to move the fins; lash the water with the fins, as a whale when dying.

noun

airfoil , appendage , arm , dorsal , flipper , hand , pinna , stabilizer , vane