That sub at Quizno's is a SILF.

Person 1:OH MY GOD, look at that chick.What a SILF.
Person 2: Dude, thats YOUR sister. That's nasty.
Person 1: It's called SILF for a reason dude. DUUU

UrbanDictionary is SILF

"BustedTees aint SILF..."

that silf lives in your house?!?

Welsh Farmer: oh, thats a mighty fine sheep
Welsh Farmer b: yes it is a silf.

I was like hey wargo, he goes what do you want, I said besides your sister and then he threw a sandwich at me in disgust