an ass that is extremely big, yet it is so sloppy because it has wrinkles or flaps of grease everywhere - Just like a Big Mac.
Guy 1: Yoo I got some ghetto booty last night! She got that big ass son.
Guy 2: Aww hell, that ain't no good ass, that's a big mac ass.
Guy 2: Aww hell, that ain't no good ass, that's a big mac ass.
by TheOtherWong February 8, 2010
Get the big mac assmug.