The excess build up of ass cheese, vaginal discharge and sweat on that of a woman’s supposed “sexy” thong. This is do to the neglect of a daily shower and/or a fresh pair of panties. It will often resemble the color and texture of dried baby vomit.
Mom - (to daughter) Go get your sisters laundry and clean them please.
Daughter - Ewww!!! Mom!!! Come look at her crusty thong. It's the most revolting thing I have ever seen.
Mom - Dear lord, mother of holey Jesus, what in the hell is that!?
Daughter - Its her thong, I think. Im not touching it, you touch it.
Mom - There is no way I am touching that disgusting thing; besides, you found it first.
Daughter - No! I might catch something and OH MY FUCKING GOD!! I think it just moved.