fin

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

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

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.

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

Organ of locomotion and balance in fishes and some other aquatic animals.

Show the fins above the water while swimming.

“The sharks were finning near the surface”

Equip (a car) with fins.

Propel oneself through the water in a finning motion.