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
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 August 27, 2008