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1.
After taking a poop the average human, chooses to wipe the anus to remove any left over excrement. When in the wiping process if on discovers that fecal matter is left on a finger, he/she has been mud knuckled.
i had some taco bell yesturday, ive been crapping all day, sloppy ones too, i even got mud knuckle it was so bad.
by mike lea January 19, 2005
 
2.
A mudknuckle is when you take a shit, smear your knuckles in it an then punch someone in the face.

Mudknuckles can be also delivered using other people's shit, dog shit, cat shit and/or tiger shit. Basically you can use any poop available.

VARIATIONS:
A Hairy Mudknuckle is when you dip your shit covered knuckles in pubic shavings before punching someone in the face.

A Mudknuckle Favor is when you smear your knuckles in shit and then pee on your knuckles to rinse some of the poop of before punching someone in the face.
Person A: I just got in a fight and now I have shit on my face. What the hell happened?

Person B: Damn B... You just got mudknuckled
by B.Ready November 30, 2010
 
3.
The Anus
Your Mud Knuckle smells.
by Gulies January 25, 2009