a smart-arse

a smart-arse

  (British very informal) also a smart-ass (American very informal)
someone who is always trying to seem more clever than everyone else in a way that is annoying OK, smart-arse, do you have a better idea? (British very informal)
References in periodicals archive ?
However I am in no position to be a smart-arse here because I too have recently been a guest on the show ( it hasn't been shown yet) and when I was asked, "In Science, what is O2?