- any of various apparatus for heating, especially for heating water or the air in a room.
- Electronics. the element of a vacuum tube that carries the current for heating a cathode.
- Slang. a pistol, revolver, or other firearm.
- any device for supplying heat, such as a hot-air blower, radiator, convector, etc
- US slang a pistol
- electronics a conductor carrying a current that indirectly heats the cathode in some types of valve
c.1500, of persons, agent noun from heat. Of devices, from 1660s. Baseball slang meaning “fastball” is attested by 1985.