When a woman with a flabby ass presses it into your face. This could be done to anally motorboat, perform analingus or cunnilingus. Can be used in both a positive and negative sense.
"How did things with that girl go last night?"
1) "They went well until she gave me the ass potato pancake"
or
An older woman's ass that is rotund and full of cellulite dimples. When they sit down, the ass seems to squish and go all over the place, as if they were sitting on a pile of mashed potatoes.