All those work. Technically it's a tractor. Some people call them Semi-Trucks, but that actually refers to the trailer. Semi means half, and the trailer is only half supported on it's own axles. The other half is supported by the tractor or a landing gear when no tractor is attached.Rachel Varga link wrote: By the way what is the proper term? big rig, 18-wheeler, or what?
So the next time a guy says he has a semi in his pants, be concerned. He's only got half a penis.