\Au`***"bile\, n. [F.] An automobile vehicle or mechanism; esp., a self-propelled vehicle suitable for use on a street or roadway. Automobiles are usually propelled by internal combustion engines (using volatile inflammable liquids, as gasoline or petrol, alcohol, naphtha, etc.), steam engines, or electric motors. The power of the driving motor varies from about 4 to 50 H. P.
An automobile is a car. Automobile is a very old fashioned word though. I can't recall ever hearing anyone use it. Car is much better. Motor car also sounds odd to a native speaker, although people might refer to their car as their motor in some parts of the UK.
An automobile is a passenger car. Trucks, buses, and tractors, etc. are considered self-propelled vehicles or motor vehicles, to differentiate them from bicycles, which are also vehicles.