Similar in nature and function to a regular bitch, however is differentiated because the bitchstress is even MORE of a bitch than the main/regular bitch. However, because the existence of the bitchstress is often shrouded in mystery and is rarely visited upon, the bitchstress cannot be considered the main bitch.
Joe: Dude you look like you got caught in a hurricane! What happened?
Bill: I just got back from seeing my bitchstress...
Joe: Woah you have one of those? I thought they were myth, you're a real glutton for punishment aren't you?