Main Entry: prime mover

Function: noun

Etymology: translation of Medieval Latin primus motor

Date: 1809

1 a : an initial source of motive power (as a windmill, waterwheel, turbine, or internal combustion engine) designed to receive and modify force and motion as supplied by some natural source and apply them to drive machinery b : a powerful tractor or truck usually with all-wheel drive
2 : the self-moved being that is the source of all motion
3 : the original or most effective force in an undertaking or work <education is…a prime mover of cultural and societal change — R. C. Buck>