Seemingly derogatory term but often used with affection. In the classic sitcom Malcolm in the Middle, the brothers call each other buttmunch but with a smile and a pat on the back. The word can also be used as a sexually suggestive term, using it on someone you would actually like to munch on your butt.

When someone goes to the gym and spends 90% of the time on their phones scrolling through social media

a term made poular by beavis and butthead, commonly referring to beavis.

Butt Munch-
1. An annoying person that you would like to shut up.
2. A bothersome sibling.
3. A friend who is being a jackass.

a very irritable person. Hence the first definition.

n. Someone who is a source of irritation, thus becoming the target of another's animosity.
Syn.: jerk, wanker, bastard, fucker, creep, buttmonkey, asshole, shithead

N. An annoying person who you can't stand. Someone you can't find a word for.