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