A big rig truck: a semi-trailer plus the truck or tractor pulling it.
The front part of a semi-trailer type truck, i.e., the tractor to which the trailer part attaches.
A person or thing that is seminal and influential.
A military or heavy construction vehicle.
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