Originally in translation of Latin primum mobile.
- (philosophy) The initial agent that is the cause of all things.
- 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
- (automotive) The front part of a semi-trailer type truck, i.e., the tractor to which the trailer part attaches.
- (US) A military or heavy construction vehicle.