You see that greasy, dirty, no-talent loser over there? The one with a filthy wifebeater who looks like he just fell out of a trailer home and thinks he can rap? That guy is a douchbag.
Another way of telling off someone that they're a damn fool or just a plain idiot. Just another little word for when you're right infront of the teacher and you fon't wanna swear. We use "douchbag"