The male genetic disposition for having a flat ass. An ass that has no POW! or lacks badunka dunk. Most commonly associated with male Caucasians, white-guy butt (or WGB) can also be found on other male members of all races.
White-guy butt is not to be confused with computer ass, which results from a lack of activity associated with hours and hours of daily computer usage.
Dude: Stupid white-guy butt, my pants keep falling down 'cause I got no ass!!!
Chicky: That's some serious no-ass WGB, yo.