prime mover

Noun

prime mover (plural prime movers)

1. The initial agent that is the cause of all things.

   Synonyms:

   first cause, first mover, primum mobile, unmoved mover

2. A machine, such as a water wheel or steam engine, that receives and modifies energy as supplied by some natural source or fuel and transforms it into mechanical work
3. Tractor unit. Or, more specifically, the front part of a semi-trailer type truck, i.e., the tractor to which the trailer part attaches.
4. (US) A military or heavy construction vehicle.
5. A person or thing that is seminal and influential.
   • "I need not remind this audience that, though Professor Summerlee, as the head of the Committee of Investigation, has been put up to speak to-night, still it is I who am the real prime mover in this business, and that it is mainly to me that any successful result must be ascribed."1912, Arthur Conan Doyle, The Lost World […], London; New York, N.Y.: Hodder and Stoughton, →OCLC
   • Seeger was a prime mover in the folk-music revival and was accepted by collegians and young people outside the South, regardless of his alleged Communist sympathies […]1986, R. Serge Denisoff, Tarnished Gold, page 381
6. An agonist muscle.