- A conductor used for indirect heating of the cathode of a thermionic tube
- (heater) fastball: (baseball) a pitch thrown with maximum velocity; "he swung late on the fastball"; "he showed batters nothing but smoke"
- A person or thing that heats, in particular a device for warming the air or water
- A fastball
- (heater) device that heats water or supplies warmth to a room
- A heater is object that emits heat or causes another body to achieve a higher temperature. In a household or domestic setting, heaters are usually appliances whose purpose is to generate heating (i.e. warmth). Heaters exists for all states of matter, including solids, liquids and gases.