Someone who builds him or herself up with a bunch of talk, but can never back up anything he or she says.
"...and then I surfed down the volcano on a piece of scrap metal, while shooting indians and alligators with my bow and arrow. All of a sudden I saw this really hot girl stuck in a tree, naked, with a pack of hungry gorillas after her, so I swung from a vine and grabbed her, then I jumped onto a passing helicopter. But the helicopter landed in Iraq and Osama bin Laden started chasing us. He shot me but I reflected the bullet off the piece of scrap metal and it ricocheted back and killed him. Then I carried her across the border and all the way to France. Where we got a hotel room and I banged her. Indabutt."
"Shut up bitch. You're all talk."