One lacking in common sense, talks rubbish, acts stupidly. Immature and without thought.
That idiot over there is embarrassing.
What people that think it was a good idea to make the majority on Urban Dictionary sexual are.
Graham: Did you hear about what Ray just did?
Luna: No, what did he do?
Graham: After he just won a tennis match just for fun against his friend, Andrew, he decided to hit the bar and slipped on an ice cube on the floor and got hurt.
Luna: What an idiot! Besides, why did he even hit the bar after the match anyway?
Graham: I have no idea, he should have just went home, where he would've been safer.
Luna: Which he would've done if he wasn't so stupid.