To mash cakes means bumping uglies, swaping gravy, or doing the no pants dance. Can be used in past tense and appreviated ex."we mashed"
If you bring home a drunk college girl from a keg party, your probably gonna end up mashing cakes.
The disastrous results of shitting yourself and seeing what the contents of your undergarments look like
Egad I've got 3 and 3/4 lbs of mashed up Dundee cake in the seat of my pants right now