{i} ass, buttocks (British Slang); someone who is stupid or repulsive (Offensive, British Slang)
Your arse is your bottom. a pain in the arse: see pain. Variant of ass. can't/couldn't be arsed (to do sth) to not do something because you are feeling too lazy arse about/around to waste time behaving in a silly way instead of doing the things you should do