When a woman/girl claims to be a virgin on the grounds that the only penetrative sex she's ever engaged in has been anal.
Jack: Dude, your girlfriend's a slut
John: No way, she was a virgin when we started dating
Jack: Yea, only cuz of the poop-hole loop-hole. Just ask Dave, Mike, Jamal, Terrence, Shaun, Shawn, Sean, and our biology teacher