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.
- 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.
- A cooling device, as in automotive engines, through which water or other fluids circulate as a coolant.
- Physics A body that emits radiation.
- A transmitting antenna.