hungry bum

The appearance of your ass crack eating up your pants and any under garments.
i.e. the pants are being pulled into the crack at an alarming rate.

Also known as a wedgie, where the underpants are drawn/forced/pulled/slipped up into the butt crack.

when you don't wear underwear and your arse eats your pants.

When a persons lower clothing rises up into their bum crack.

Noun.
Hungry bum, is a state that your bum goes into. Essentially, it is when one's ass hole tries to swallow that person's undergarments. This state can aslo happen (in some cases) where there is execcive bum hair. The ass hole attemps to devour the hair.

The act of a womans or mans underwear or bathingsuit getting swallowed by their buttox. In worse situations it may be referred to as a starving bum. Usually this happens for larger ladies that wear too small of bathinsuits because they think its attractive to look at cottage cheese.

When a person's pants/jeans/shorts are riding up the butt in an unattractive fashion requiring a "manual release" of sorts - usually happens to overweight women (but not exclusively). It looks like the bum is literally eating the pants.