The ultimate insult you could bestow upon anyone who talks bullshit all the time. as a double whammy this word also means the explosive matter that could come out of the ass at such great speeds that it seems like your arse has been out drinkin to much last night.
Person 1: So I saved the entire population of Ireland with a string and a folk!
Person 2: Bullshit you did you buttchuck!
Man I had the biggest buttchuckin session last night!