lifting belly
When a character's belly is raised by their own, or another character's hands. In most cases, this involves the "belly owner" to be slightly chubby, overweight or obese.
The character may be simply playing with their belly, examining their "fatness", presenting their belly, or be exposing their crotch that would otherwise be covered by their large belly. The acting of lifting a belly may lead to a belly drop — when a character lifts and then drops a fat belly