Someone (usually a guy) who tries to be overly macho and cool, but instead comes off ass being an asshole.
This often takes place when the speaker is trying to impress a girl, but lacks the proper social skills.
Dude 1 (to girl 1): Hey, wanna suck my dick? I know you do. I mean, I've got the hugest dick in this whole place...not like Dude 2 over here.
Dude 2: Dude! Not cool.
Girl 1: It's ok, he's just being a badasshole.