be a pain in the arse(redirected from be a pain in the backside)
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!