Arse

Arse is British slang expression for buttocks. It is not a very nice word.

HOWEVER it must not be forgotten that Arse is an Anglo-Saxon word taken over to the New World by the Pilgrim Fathers. Once there they seem to have lost their ability for discrimination, hence the current colonial (i.e.US) corruption of the word Arse into the current usage Ass, which in Britain still refers to a donkey. So when colonial boy says he is an Ass man, then perhaps you would be justified in looking askance.