A noun used to describe sexual
intercourse - is usually used by someone who has an
obsession with
sharks or sea creatures.
Can be used interchangeably with the word ass.
Kyle: I was gettin' some fin last
night - it was hot!
Morality Preacher: Whoa, whoa
little pup - you're not even a shark yet. You should wait a few years before tappin' that fin ;)
Kyle: Yay Morals!