When you're having sex with a fat person, you slide your penis inbetween their folds of fat until you climax into the belly button.
Person A: "You had sex with someone THAT fat?!"
Person B: "Yeah! It gave me the chance to do a Matt Nasty!"
Person B: "Yeah! It gave me the chance to do a Matt Nasty!"
by Bryan Z. July 28, 2006
Get the Matt Nastymug. An overwhelmingly disgusting, and sometimes funny male named Matt. Who roams myspace hitting on and insulting females. He bakes "e-cookies" or whatever. Also he spams the myspace chat rooms like an immature little child.
by matt543111 October 16, 2008
Get the Nasty Mattmug.