TransFormers which have a Nebulan (humanoid) companion who transforms into the head of the transforming robot, and does not form part of (but can usually drive or otherwise connect to) the large robot's vehicle and/or beast mode/s.
Sometimes used to mean the large robot, sometimes the small figure/head. (Japan only: some heads were brought out without bodies, and all heads were interchangeable between robots, making more sense of the term "headmaster").
Of course, it also means a male head-teacher (now rarely used for PC reasons) - presumably it's a play on words (used as a model for later names such as Powermaster, Targetmaster etc.). Initially appeared in series 4 of
generation 1.
Also, the first series of the Japanese
Transformers cartoon (the 4th series overall) is called "TransFormers Headmasters".
