muddy knuckles 

when a person shits on another persons face and then punches that person in the face...resulting in muddy knuckles

also could be after fisting an ass and resulting in muddy knuckles

bitch you keep sass'n me were gonna play muddy knuckles

muddy knuckles by bukake_ninja June 24, 2008

Muddy Knuckle

Anal fisting: where some one inserts a clenched fist into someones anus.

Clarissa's bum hurt after her boyfriend gave her a muddy knuckle.

Muddy Knuckle by Rhyzzzzzzzzzzzzzzzzzz December 1, 2009