The act of having a nervous attack over a small event; freaking out to the point where everyone thinks you're a pansy.
When he saw the spider in his room, he totally vagged out and asked his girlfriend to kill it.
Dude, she totally didn't mean to defriend you on Myspace; quit vagging out.
When a guy has inane, extended phone conversations with his girl instead of hanging out with the fellas.
Gregg: Yo, where's Luke, I thought we were getting shitfaced together.
Doug: Not gonna happen man. He's busy vagging out in his room.