When you solidify semen by freezing it into nugget shape, then insert it into a woman's anus, waiting for it to melt and leak out before being served to the man eating ass.
Person 1: Last night, my girl made me some tasty anal nutnuggets, it was great.
One who finds great pleasure in farting;releasing noxious fumes from their ass to the point where they either drop a buttnugget in their pants or on the floor
Keith: Oh man! You smell that?
John: Yeah, you need to go the bathroom!
Keith: No, I'm good for now. (keith farts again). Wow! That one felt good!
John: Dude! Go to the bathroom!
Keith: I think I'm done. (keith farts one more time). Oh wow! That one felt great!
John: Keith..one more time - go to the bathroom!
Keith: Oh man.. I just shit my drawers
John: You're such a masturbatorial buttnugget.
Keith: I'm going to the bathroom now.
Small piece of fecal matter left lodged in anal opening when defacation does not exit in a generally whole piece. Usually requires tissue to dislodge or waiting of gravity to dislodge itself.
John has to wipe his assseveral times because when he shitted, he was left with a buttnugget