this term refers to any manner of snack cakes. most popularly, these come in the form of various 'little debbie' brand creations not limited to 'zebra cakes', 'fancy cakes', and the ever-present 'swiss cake rolls'
A slpppycake occurs when you blow your load in your hand then slap your partner in the face.
I knew she was about to reach orgasm, as was I. She was so turned on, I pulled out, shot my wad in my hand, and gave her a slappycake. She came immediately...