Source : Webster's Revised Unabridged Dictionary (1913)

Radiator \Ra"di*a`tor\, n.
   1. Any of various devices for cooling an internal substance
      by radiation, as a system og rings on a gun barrel for
      cooling it, or a nest of tubes with large radiating
      surface for cooling circulating water, as in an
      automobile.

   2. (Wireless Teleg.) An oscillator.

Radiator \Ra"di*a`tor\, n.
   That which radiates or emits rays, whether of light or heat;
   especially, that part of a heating apparatus from which the
   heat is radiated or diffused; as, a steam radiator.

Source : WordNet®

radiator
     n 1: any object that radiates energy
     2: heater consisting of a series of pipes for circulating steam
        or hot water to heat rooms or buildings
     3: a mechanism consisting of a metal honeycomb through which
        hot fluids circulate; heat is transferred from the fluid
        through the honeycomb to the airstream that is created
        either by the motion of the vehicle or by a fan