1.someone absolutely annoying, bothersome
2. A little chunk of poo with beans in it
1. OMG evan is such a buttchunk.
2. You should have seen this gross buttchunk i left in the toilet
Typically used by people who want to find a creative way to use the word "butt" in an insult that isn't "butthead" or "butthole."
Not literally referring to a chunk of a butt.
Andy ate the last oreo again. God, he's such a buttchunk.