fin

the cardinal number that is the sum of four and one

one of a pair of decorations projecting above the rear fenders of an automobile

one of a set of parallel slats in a door or window to admit air and reject rain

a shoe for swimming; the paddle-like front is an aid in swimming (especially underwater)

a stabilizer on a ship that resembles the fin of a fish

organ of locomotion and balance in fishes and some other aquatic animals

equip (a car) with fins

propel oneself through the water in a finning motion

show the fins above the water while swimming; "The sharks were finning near the surface"