Ass to pussy ratio. The ratio at which a female will have anal sex versus vaginal.
Guy I: A man whats Kim's APR as of last night?
Guy II: 3 to 1. I think she's starting to like it more and more.
Girl I: Shit, my APR went up last night. Its now 2:1
Girl II: Damn, I didn't know you were that kind of freak.