When you pull out during intercourse and cum onto a girl's (or guy's) stomach, resulting in their belly button filling up with sweet jizzum. That jizz can then be sucked out and enjoyed like a body shot.
Jizz + Belly = Jelly Shot
Ali: So where do you want to blow your load?
Babe: Right in your belly button, so I can make your mom come and take a Jelly Shot.