A long vehicle built to carry other vehicles. The classic picture is the double-decker lorry loaded with brand-new cars, driving from the factory to the showroom — that is a car transporter. There are also military tank transporters and, at airports, transporters that carry aircraft parts.

Outside that main meaning, the word stretches in a few directions. Any large vehicle or machine that moves goods can be called a transporter in technical writing, and there is a famous 'transporter bridge' in some British cities — a bridge that carries a moving platform across a river with cars on it.

Two other uses are worth knowing so you are not confused when you meet them. In science fiction — Star Trek especially — a transporter is the machine that makes people disappear in one place and appear in another ('Beam me up'). Many young English speakers meet the word there first. And in biology, a transporter is a protein that carries substances across a cell membrane.

The everyday vehicle sense is plain and neutral, used by drivers, logistics companies and news reports. British English uses it more than American English, where 'car carrier' or 'car hauler' is common.