fins Share definition Flag 5 dollar bill in canada or a 5 peice (.5 grams of weed) Guy1-"yo I got a fins, I just have to go pick it up" Guy2- "Why not call up crazy joe, he delivers" fins by Bo Vicious August 2, 2007 0 0 Get merch Get the fins mug. Buy Now — $32.95 See more merch