Refers to any tight white pants worn by a male or female, which are often see-through. These tight white pants denote that the wearer is slutty and thus, open for business. Often worn by whores and Surrey girls. Furthermore, it can refer to the person wearing them.
Slut pants are those plad PJ pants that people think are ok to wear in public. All it really means is the person wereing them is ready for sex. easy down easy up, perfect for quicky.
Dude1: dude you see that chick, shes totaly read for it just look at her slut pants they aleady have splougemarks on them.