When a chubby person wears a shirt that is too tight for them, and the material stretches tightly over the large recess in their stomach which leads to their bellybutton. The tightly pulled material yields a 'trampoline' effect over that area.

Tight fabric over the belly button crevice of muffin tops. bounce on that shit, yo.
That fat chick has some serious bellybutton trampoline going on with that shirt.
by h4xp0ck3tz January 16, 2014
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