1. A baked confectionary sandwich consisting of icing or some other sweet, creamy filling between two round pieces of cake, typically chocolate. More commonly called a "whoopie pie." My mom used to make whoopie cakes for us as a special treat at the end of the school year. Oh wow, whoopie cakes! I didn't know you could find these outside of Pennsylvania!
2. slang One's buttocks. (Used in the plural.) Thomas! Get your whoopie cakes in here right now and clean up this mess! I don't know what she's thinking wearing that outfit. Her whoopie cakes are practically hanging out of it!
n. female buttocks. You put those whoopie cakes back down in that chair and listen to me!