Adjective. When a girl is so loose and stretched out that when you are having intercourse you need to ask her "is it in you?". Usually is the result of years of sluttiness or perhaps having a lot of children.
Friend 1: How was that dancer you brought home last night?
Friend 2: Great to look at but definetely a gatorade girl.
Hey let's go to the bar, order up some gatorade and make some bad decisions