be a pain in the arse(redirected from be a pain in the butt)
be a pain in the arse
rude slang To be an especially irritating, aggravating, or obnoxious person, thing, or situation. Primarily heard in UK. You know, Jack, you may be my friend, but you can be a real pain in the arse sometimes! This calculus homework is a real pain in the arse. It's not that I don't understand it, it's just so tedious!
be a pain in the arse/backside(British & Australian very informal) also be a pain in the ass/butt (American & Australian very informal)
to be very annoying I can't stand my brother-in-law. He's a real pain in the arse. Getting up for work at 5 a.m. is a pain in the ass.