On a steam locomotive, a powered wheel driven by the locomotive's pistons or turbine.
In machinery, a principal wheel that communicates motion to some other or to others.
In railroading, the big wheels (generally four, though sporadically as many as ten, in number) in a locomotive engine that are fixed upon the crank-axles or primary shafts. Also known as driver and drive-wheel.
a wheel that drives a motor vehicle (transforms torque into a tractive force)
a wheel that communicates motion; one of several big rims of a locomotive to which the connecting rods associated with the engine tend to be connected; -- labeled as also, merely, motorist. See Illust. of Locomotive.