Used to describe people that try too hard to be "cool", people that try to get attention by doing something "cool", or people that show off or act cocky in a miserable attempt to impress others.
Rick: Look at that intense guy walking around without a shirt on.
Steve: Yeah, he's so intense....
Tran: Why did that guy just speed by us in his piece-of-crap car?
Esteban: Because he's really intense.