The dark patches of skin found between a fat girl's thighs and ass, which can be caused by poor circulation and the kidneys and liver not operating efficiently.
Tony: "Man, I think Lisa is so fucking Sexy! Is she good in bed?"
John: "Fuck, yes! But don't mind the pig stains!"
Tony: "Damn! I know she's fat, but if she's got pig stains, she's a little too fat for me!"