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1. Marshmallow Surprise
A sex act where midway through intercourse the male defecates into a sock and shoves it into the females mouth.
guy: dude I gave my girlfriend a marshmallow surprise
guy2: nasty
2. Marshmallow Surprise
A seemingly delicious treat made from sprinkles inside mini marshallows inside larger marshmallows.
"Do we have marshmallows for the campout tonight?"

"No, Kara took them all so she could make Marshmallow Surprise."