1.the cardinal number that is the sum of four and one
2.one of a pair of decorations projecting above the rear fenders of an automobile
3.one of a set of parallel slats in a door or window to admit air and reject rain
4.a shoe for swimming; the paddle-like front is an aid in swimming (especially underwater)
5.a stabilizer that resembles the fins of a fish
6.organ of locomotion and balance in fishes and some other aquatic animals
1.equip (a car) with fins
2.propel oneself through the water in a finning motion
3.show the fins above the water while swimming;
The sharks were finning near the surface