look up any word, like sex:
A fish knuckle is when a woman masturbates vigorously to the point that her "natural" feminine odors now permeate directly off of her knuckles.
After 2 hours of abusing her pussy to pictures of The Rock, it appears as if Cindy is now suffering from fish knuckle.

Big lipped Jamal wasnt sure if Shaniqua ate catfish for lunch or had the fishknuckle.
by Wrestling SOup November 28, 2012
A shaved camel-toe.
So Cindy shaved last night, that was the best damn fish knuckle I've ever had.
by GurrBurr August 20, 2010