[prime mover] n [trans. of ML primus motor] (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 usu. 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"