A woman/man who works behind the bar in a strip club and regularly masterbates over the strippers.
Man: I once had a girlfriend, she was a megawhore. She'd come back from work so wet, I could collect her fadge juice in a cup and use is as lube for the serious buggeration she recieved afterwards.
Woman: My husband is a megawhore, he loves his job an awful lot. God knows what he gets up to.
A girl who is unfaithful, untrustworthy, and a complete waste of your time. a girl who is an easy lay, a girl who cheats, a girl who is pretty and manipulative, a girl who needs a life, and a girl recently fucked over and wants to use you as a rebound guy.
i.e. girls named megan(sometimes with bestfriends named selena, nikki, or taylor)
John:Im a virgin
Megan:We can fuck on valentines day even if i have a boyfriend...
Boyfriend:i guess you didnt change, Megawhore...