radiator

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A heating device consisting of a series of connected pipes, typically inside an upright metal structure, through which steam or hot water is circulated so as to radiate heat into the surrounding space.
• noun A cooling device, as in automotive engines, through which water or other fluids circulate as a coolant.
• noun Physics A body that emits radiation.
• noun A transmitting antenna.

from The Century Dictionary.

• noun Same as cooler, 2 .
• noun In the transmission of electric waves, as in wireless telegraphy, an apparatus for the emission of electric oscillations; a form of oscillator.
• noun Anything which radiates; a body or substance from which rays of heat emanate or radiate.
• noun A part of a heating apparatus designed to communicate heat to a room, chiefly by convection, but partly, in some cases, by radiation.

from the GNU version of the Collaborative International Dictionary of English.

• noun 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.
• noun Any of various devices for cooling an internal substance by radiation, as a system of 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.
• noun (Wireless Teleg.) An oscillator.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Anything which radiates or emits rays.
• noun Automotive A device that lowers engine coolant temperature by conducting heat to the air, through metal fins.
• noun A finned metal fixture that carries hot water or steam in order to heat a room.
• noun electronics A type of antenna.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun any object that radiates energy
• noun heater consisting of a series of pipes for circulating steam or hot water to heat rooms or buildings
• noun 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