A female that has taken disgust and grime to an extremity, a true whore at heart that reminds every man of something that can be purchased at mcdonalds; fat, sloppy, and down right disgusting. Generally, if you are indeed dealing with a true McNasty on your hands, chances are that she is so loose that a football can get inserted with zero difficulty.
Guy 1: Wow bro, every time I turn around that girl is hooking up with a new guy. I can't believe you got with her!
Guy 2: I know dude! Chances are I might have an STD...Im pissed.
Guy 1: Yeah dude I'd get checked out tomorrow, what a god damn McNasty