An acronym for "15 And Fuckable." Typically used to describe an attractive teenage girl/lolita that one would readily fornicate with. Can be modified for alternate ages with alternate adjectives (e.g., 16AS = "16 And Suckable," etc.)
Originates from an inside joke amongst a group of technicians at a popular American theme park.
"Yeah, I was walking through the waterpark and I saw a couple 15AFs that definitely needed to be introduced to my dick."