[M]
mech fluid- noun: an essential liquid in the Transformer's body of unknown use and purpose; possible Transformer equivalent of blood, along with energon
megacycle- noun: Cybertronian measurement of time, roughly equivalent to one Earth hour
Metacycle: 13 months
Metallikato: The cybertronian martial arts style used by G1 Bludgeon.
mouthplate- noun: protective metal mask which covers a Transformer's face from the jaw up to (and occasionally including) the "nose"; see also: faceplate; alternately, the Cybertronian idiomatic equivalent of "lips" (e.g., "Quit flapping your mouthplates and get serious!")