Taking one roll of fat on one side, inserting dick and then on the other side of the dick put another roll of fat. Then thrust. Basically a titty fuck with fat.
Me- You guys do anything last night?
You- Not much, but I fat fucked the shit out of her!
Me- What could you not find her vagina?
1.) A person who is fat and is also considered lazy.
2.) A woman with a visually stimulating buttocks (see: booty). The two-word combination might also be spelled "Phat Ass", litterally meaning that the ass is "phat".
Man at club 1: Damn, she's got a fat ass!
Man at club 2: I know negero!