From WordNet (r) 2.0 (August 2003) [wn]:
automobilist
n : someone who drives (or travels in) an automobile [syn:
motorist]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Automobilism \Au`to*mo"bil*ism\, n.
The use of automobiles, or the practices, methods, or the
like, of those who use them. -- Au`to*mo*bil"ist, n.
[Webster 1913 Suppl.]