What is the meaning of the word "fin"?

Definitions:

a shoe for swimming noun
- I put on a pair of fins before I went snorkelling.
a stabilizer on a ship that resembles the fin of a fish noun
- I scraped barnacles off the fins of my new boat.
one of a pair of decorations projecting above the rear fenders of an automobile noun
- Fins on the back of your car were very popular in the 1950s.
one of a set of parallel slats in a door or window to admit air and reject rain noun
- My new door had fins made out of mahogany.
organ of locomotion and balance in fishes and some other aquatic animals noun
- Some fish have pectoral and dorsal fins.
to equip a car with fins verb
- I finned my new racer.
to propel oneself through the water in a finning motion verb
- I finned quickly in the pool.
to show the fins above the water while swimming verb
- The sharks were finning near the surface.