prime mover

Meanings

1. The initial agent that is the cause of all things.
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. A military or heavy construction vehicle.
5. A person or thing that is seminal and influential.

Etymology

Originally in translation of Latin primum mobile.