Acronym: Last Resort. The worst kind of hook up there is, but still absolutely necessary. Usually a girl/guy who is less than average in terms of attractiveness and has no life so as to be available for hookups whenever needed.
Girl #1: So how was last night?
Girl #2: Terrible. I was so horny and my usual was out of town, and the only one who was available was my LR.
Girl #1: I'm so sorry
Girl #2: So am I