A real smutty girl, one who is down for the team. If you and your boys are at the lunch table and you see a girl walk by and all of you can say that at one point each of you have fucked her, she's probably the act.
also known as The Action
E: Yo my boy I just fucked that one bad jawn from math class.
J: Shit, that aint nothin I done hit that like 5 times already, shit a lotta dudes have to be honest, she's the act!