A slice of asspie, as it is commonly referred to, is a synonym for a big, steaming pile of shit. To qualify as an asspie, the crap must be larger than a Volkswagen Beetle spare tire and it must be fresh. Extra points if there is actual steam rising from it!
John: This movie was a piece of steaming asspie!
Elizabeth: Have you seen 2 girls 1 cup? That bitch cranked out an asspie in a cup.