The Collaborative International Dictionary of English v.0.48:

Automobile \Au"to*mo*bile`\, n. [F.]
   a self-propelled vehicle used for transporting passengers,
   suitable for use on a street or roadway. Many diferent models
   of automobiles have beenbuilt and sold commercially,
   possessing varied features such as a retractable roof (in a
   convertible), different braking systems, different
   propulsion systems, and varied styling. Most models have four
   wheels but some have been built with three wheels.
   Automobiles are usually propelled by internal combustion
   engines (using volatile inflammable liquids, as gasoline or
   petrol, alcohol, naphtha, etc.), and sometimes by steam
   engines, or electric motors. The power of the driving motor
   varies from under 50 H. P. for earlier models to over 200 H.
   P. larger models or high-performance sports or racing cars.
   An automobile is commonly called a car or an auto, and
   generally in British usage, motor cars.

   Syn: car, auto, machine, motorcar.
        [Webster 1913 Suppl. +PJC]

The Collaborative International Dictionary of English v.0.48:

auto- \au"to-\ [Gr. ? self.]
   1. A combining form, with the meaning of self, one's self,
      one's own, itself, its own.
      [1913 Webster]

   2. a prefix with the meaning of self-moving, self-propelling;
      as, an autocar, an autocarriage, an autotruck, etc., an
      automobile car, carriage, truck, etc.
      [Webster 1913 Suppl.]

The Collaborative International Dictionary of English v.0.48:

auto \au"to\, n. [Gr. ? self.]
   An abbreviation of automobile.

   Syn: car, automobile, machine, motorcar
        [Webster 1913 Suppl. WordNet 1.5]

The Collaborative International Dictionary of English v.0.48:

auto \au"to\, a.
   of or pertaining to an automobile; as, an auto mechanic.
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

auto
    n 1: a motor vehicle with four wheels; usually propelled by an
         internal combustion engine; "he needs a car to get to work"
         [syn: car, auto, automobile, machine, motorcar]

Moby Thesaurus II by Grady Ward, 1.0:

87 Moby Thesaurus words for "auto":
   PCV valve, accelerator, alternator, ammeter, autocar, automobile,
   bearings, boat, bonnet, boot, brake, bucket seat, buggy, bumper,
   bus, camshaft, car, carburetor, charioteer, chassis, choke, clutch,
   connecting rod, convertible top, cowl, crank, crankcase,
   crankshaft, crate, cutout, cylinder, cylinder head, dash,
   dashboard, differential, distributor, exhaust, exhaust pipe, fan,
   fender, flywheel, gear, gearbox, gearshift, generator, headlight,
   headrest, heap, hood, horn, ignition, intake, jalopy, machine,
   manifold, motor, motor vehicle, motorcar, motorized vehicle,
   muffler, parking light, pilot, piston, power brakes,
   power steering, radiator, rear-view mirror, ride, seat belt,
   shock absorber, spark plug, speedometer, springs, starter,
   steering wheel, tool, top, transmission, tub, universal, valve,
   voiture, wheel, wheels, windscreen, windshield, wreck