A robotic model of an attractive woman designed to secretly assassinate a particular target, most often it's Austin Powers. Fembots have a very easy method of identification if you should suspect that a woman is really a fembot. You can always tell a fembot by the machine guns that pop out of their hooters immediatly before trying to shoot and kill you.

Also, according to Mike Meyers in the Austin Powers 2: The spy who shagged me DVD commentary soundtrack, the term "fembot" was stolen from The Six million Dollar Man

Note: fembot should not be confused with Femalien