1. One who is sarcastic or makes jokes in an attempt to seem witty, usually to others' annoyance; a smart aleck. Joe is such a wise guy that it's hard to know when he's being serious.Every class seems to have one disruptive wise guy.
2. A mobster. I wouldn't bother those shady characters sitting in the corner booth—they're all wise guys.
An obnoxious know-it-all, a person who makes sarcastic or annoying remarks, as in the teacher was delighted that the worst wise guy in the class was moving out of town. [Slang; second half of 1800s] Also see smart aleck.