humping belly

When a character is thrusting their hips to rub/grind their genitalia against their own, or another character's belly.

When a character is humping their own belly, they are usually resting atop their own massively bloated belly; characters masturbating in this way is especially common in same size vore content.

A character humping another's belly may be straddling or sitting on top of the character's belly