A heater is any object that emits heat or causes another body to achieve a higher temperature. In a household or domestic setting, heaters are commonly used to generate heating (ie. warmth). In electronics, the term may refer to the filament in a vacuum tube that heats the cathode to aid in thermionic emission of electrons. Also: American slang (mid-20th cent.) for a handgun. Types of heaters Block heater Cathy heater Central heater Convector heater Dielectric heater District heater Elect… (More on Heater)