n the cardinal number that is the sum of four and one
n one of a pair of decorations projecting above the rear fenders of an automobile
n one of a set of parallel slats in a door or window to admit air and reject rain
n a shoe for swimming; the paddle-like front is an aid in swimming (especially underwater)
n a stabilizer on a ship that resembles the fin of a fish
n organ of locomotion and balance in fishes and some other aquatic animals
v equip (a car) with fins
v propel oneself through the water in a finning motion
v show the fins above the water while swimming