arse
n. countablen. the part of your body that you sit on. It is also used to describe someone who is very annoying or stupid. This word is rude and mostly used in British English.
n. the buttocks or the anus. Often used figuratively to describe a contemptible or foolish person. Primarily British in usage and considered vulgar or offensive in many contexts.
He fell right on his arse.
The manager was acting like a total arse during the meeting, shouting at everyone for no reason.
From Middle English ars, ers, from Old English ærs, ears, from Proto-West Germanic ars, from Proto-Germanic arsaz (compare Dutch aars and German Arsch), from Proto-Indo-European *h₁órsos (“backside, buttocks”).
Commonly used in idiomatic expressions like 'can't be arsed' (to lack motivation) or 'pain in the arse' (something annoying).
He is a big assHe is a big arseLearners often mix the British 'arse' with the American 'ass'; while they share a meaning, 'arse' is specific to British and Australian English.