Top definition
To slip one's knuckle into the crack of an unsuspecting victim. Similar to a credit card but using the knuckle.
by akellz April 17, 2012
2
A girl who is so skinny, most likely from anorexia, that when she wears a bikini you can see the bones of her pelvis move around in her ass when she walks because she has almost no butt cheeks.
by Joe July 27, 2003
3
Jeremy's motto is "your not gay if a girl is doing it to you. Guess you can say he's a knuckle butt.
by Ballard757 January 29, 2011