What is Fast Girl?
1.
can be either someone whos a slut( or at least gives the idea that she's easy) and/or a really fast runner
( usually the best is a combination of both, but being more of a flirt than actually putting out)
"fast girls finish first" -nike running shirt
See
2.
A girl who is knida whore-like and easy to get in the sack.
"Man, that Ashley really is a fast girl" "Yeah man, I fucked that bitch up the wall the day I met Her!"
See