Prime mover
WordNet
noun
(1) An agent that is the cause of all things but does not itself have a cause
"God is the first cause"
WiktionaryText
Noun
- The initial agent that is the cause of all things.
- A machine that transforms energy from thermal or pressure form to mechanical form; typically an engine or turbine.
- The front part of a semi-trailer type truck, i.e., the tractor to which the trailer part attaches.
- A military or heavy construction vehicle.