The condition of having an asshole itch so intense and deep that it feels like the only way you can properly scratch it is to stick your finger up your ass all the way up to the knuckle, and scratch your asshole from the inside.

A case of knuckle ass might be the result of poor hygiene (see hanus anus) or could just be an unlucky ass itch that anyone can get from time to time.
"I took a shit this morning and I guess I didn't wipe well enough. Now I've got major knuckle-Ass"
by smrtpntz November 11, 2011
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When you make a fist with your hand and u rub the knuckles on the frame of an asswhole or in the ass.
by Uk36yeahaight March 3, 2019
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The growth of an inflammed, festered, and bloody hemorrhoid that creates a groove-like affect in your feces.
Dave, don't do it. Jeff has an ass knuckle, that's not going to be fun.
by Sean Piner October 1, 2006
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Someone who is clueless or stupid.
"Dude the new guy is such a dumbass!

"for real, he's a total friggin' ass-knuckle!
by Skin bone May 21, 2011
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