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 splouge marks on them.
A sarcastic expression addressing someone who looks or acts in an unbecoming way. They never understand...
Person 1: Nice pants
Person 2: Thanks! I thought my mom's neon green spandex would make an excellent fashion statement today even though I'm a 25 yearold male.
Person 1: Nice pants
Person 2: Does that mean you want to sleep with me?