A woman or in fact occasionally a man who will not admit to either intentionality or unintentionally being a whore A closet whore will flirt with EVERYONE but never admit or be aware of doing so. He/she is usually someone quite unexpected and who manages to keep most of their promiscuous behaviour under the radar!
Geeky, swatty chick: Lets play house! i'll be the door and you can slam me all night! I'll have to swear you to secrecy though!
Boy: umm okay sure!
Eavesdropper: Omg you are such a closet whore!