(v.) The act of a person's belly, sides, and back fat overflowing the boundary of his or her belt in the way a baking muffin expands out of it's cup. First used by Scott Adams (author of "Dilbert" cartoons).
Once we were on the subway,... my wife sat next to a guy who eventually fell asleep and slumped on her. I picked a guy who was muffin-topping into my seat and listening to an iPod. We felt blessed with our choices.
(Verb) The act of locating an obese person whose stomach fat protrudes at least 4" below the waistline, pulling their shirt above their head so as to immobilize them, then proceeding to pummel them with an open bag filled with a mix of sugar, cinnamon, and flour so as to generously it to the flop sweat under and around the many folds on their body.
Dude! We saw that jerk from the party last weekend and gave him a good muffin topping at the concert last night!