The Beodeker Effect: When you are checking out a girl from behind and have not seen her face yet and she looks like an eight or better on the classic ten scale of hotness, then when she turns around her face and front are a three.
Also see hot ass ugly face.
Named after the man who thought up the effect. The Beodeker.
That girl over there looked like a real hotty but then when she turned around the Beodeker Effect took affect. Damn.