It's a "semi" trailer because it doesn't have its own engine, front axles and wheels, transmission, and so on. Thus, "semi-truck" is a nickname for a truck that carries a semi-trailer.
SEMI meaning: 1 : 54114; 2 : 3 / ˈsɛˌmaɪ/ US : a short, heavy truck that has a long trailer attached to the back and that is used to move goods : semitrailer
WICKENBURG, AZ (AZFamily) — A good Samaritan jumped into action to save a semi-truck driver after the truck slammed into an RV parked on the side of the US 93 near Wickenburg on Monday. The northbound ...
KGW on MSN: All lanes open after semi-truck crash on Interstate 5 at Macadam Avenue
A crash involving two semi-trucks closed lanes on the I-5 for several hours.
All lanes open after semi-truck crash on Interstate 5 at Macadam Avenue
Yahoo: Semi truck wheel falls off, kills driver along I-64, MSHP says
Yahoo: Semi truck and sedan collision results in fatality on I-26 Saturday morning, SCHP says
Semi truck and sedan collision results in fatality on I-26 Saturday morning, SCHP says
Semi trucks are massive pieces of equipment powered by massive diesel engines (not gasoline V8s). They're also designed to haul large loads, with some of these tractors — the front of the truck that ...
Electrek: Volvo updates its electric semi truck lineup with up to 700 km range
Volvo is expanding its electric trucking lead with the launch of new and improved line of electric semi trucks with up to 430 mile range.
Volvo updates its electric semi truck lineup with up to 700 km range