(informal American) a person who seems obnoxious and irritating due to their talking or behaving as though they know everything or their pretending to be very smart;
e.g. She can be a wiseass sometimes, which makes some people dislike talking to her.
(adjective)
smug or clever in speech or manner, in a way that seems irritating and often rude;
e.g. They were tired of his wiseass comments and wished he would contribute something useful.