(1):
(n.) A projecting plane or fin on a gliding boat to lift the moving boat on top of the water; also, a gliding boat.
(2):
(n.) A plane, or any of a number of planes, projecting from the hull of a submarine boat, which by being elevated or depressed cause the boat, when going ahead, to sink or rise, after the manner of an aeroplane.
(3):
(v. i.) Of a boat, to plane (see Plane, below).