When you pay a Gentleman of Significant Stature (a fatty) the sum of $35 to spread the cheeks of his buttocks, sit on your face and flatulate. The act becomes a Filthy Marshmallow if the large man defecates, intentionally or otherwise.
Pardon me Louie Anderson, I have thirty-five American dollars and I would like to have a good time. Would you be interested in giving me a Dirty Marshmallow?
A loud and usually sleep deprived Male, who's favorite pastime is to watch Puerto Rican females twerk (shake and/or pop) her booty while riding/grinding on him during sexual activities. Or, to ride around in his bright colored car and mock/agitate the county police officers.
There goes Neal, he's such a Dirty Marshin, in his yellow car while flipping the bird at police with his twerking girlfriend.