(thong-creet) The crusties that accumulate on one's thong after a period of not wiping. Can be either a man or woman, there is no discrimination on who wears thongs and accumulates thongcrete. Most normally associated with someone who is dirty and does not shower (or in this particular case, wipe). Kind of like fumunda cheese.
Fuck man, I've got some nasty thongcrete going on.