noun: refering to the knuckle on your finger that, when inserted into the rectum of your sexual partner will cause them to expel gas around your finger and out their ass
by free42night August 24, 2006
It's reference is to someone who is dumb as a bag of hammers and/or is dense. It's when your knuckle smells like your ass because your finger is shoved up there.
by wolfhound61 October 3, 2017
the fart resulting from intense fist knuckle action. The fart's intensity and smell is equal to the depth and size of the knuckles.
a. wow his hands were so big, i got some gnarly fart knuckles.
b.guy: dude did you just fart knuckle?
other guy: yes, yes i did.
guy:smells like he knew what he was doing.
b.guy: dude did you just fart knuckle?
other guy: yes, yes i did.
guy:smells like he knew what he was doing.
by JuniorBaconCheeseBelly July 12, 2010