Condensed form of "pro-fucker". A pro-fucker can be anyone from a prostitute who gets paid to perform
sexual acts to an amateur
high school slut. A "profo" typically sleeps around and is
almost always considered "easy".
"Profo" can be used when talking about a whorish girl or it can even be used to describe a guy who gets around as well.
Female Use-
Becca: "Hey Taylor, did you hear that Sue hooked up with 4 boys last night at that
frat party?"
Taylor: "Four?! Damn, what a profo."
Male Use-
Becca: "I heard back in high school Eric had a new
girl friend every other week."
Jeff: "Yeah, Eric used to be a huge profo."