Marshmallows that an extremely attractive female deficates when a man hits her G- Spot during sexual intercourse; may occasionally taste like cellery.
Dude, check this shit! When I was boning your sister last night, she came so hard she totally busted a buttmallow!
by Thisus A. S. Yudonum April 22, 2009
1 more definition
The two cheeks making up one's ass. Buttocks.
Kathleen was too busy toasting her buttmallows by the fireplace to worry about the ringing phone.
by Boozy Tang December 12, 2007