When one's ass looks like they are wearing a diaper. Most seen on females, very rare for a male to have a diaperass.
A diaperass could also be extremely saggy butt cheeks
as long as your ass looks like a diaper.
A way to show off the diaperass look is pulling your pants up higher than normal.
1. I dare you to go tap that diaperass.
2. Why do I have such a diaperass?