a pain in the arse
a pain in the arseBRITISH, INFORMAL, VERY RUDE or
a pain in the assAMERICAN, INFORMAL, VERY RUDE
COMMON If someone or something is a pain in the arse, they are very annoying. These people were an almighty pain in the arse to deal with. Note: The words bum and backside can be used instead of arse and the word butt can be used instead of ass. When I was bored, I was a pain in the bum. All this airport security's a pain in the butt. Note: `Arse', `ass', `backside', `bum' and `butt' are all informal words for `bottom'.