when one is fat enough that the bellybutton is surrounded in fat and belly button has enough fat surrounding it for it to become large enough to stick a penis into the hole and fuck it.
i don't know if i am fucking a vagina or a bellybutton but it feels damn good... i am a bellybutton fucker
when you're holding up your phone and making faces at it, as though you are taking a selfie, but you're really taking a picture of the person across from you or the wall or anything else that seems interesting but you don't want to be caught dead taking a picture of.
This action is often made more convincing by wiggling the eyebrows or opening the mouth, to pretend you're trying to get a Snapchat filter to work.