Boiler
Part of speech: noun
Definition: An apparatus that generates heat (usually by burning fuel) and uses it to heat circulating water (or sometimes another liquid) in a closed system that is then used for space heating, swimming pool heating, or domestic hot water or industrial processes. Less commonly, a hot water heater. (approximate definition) A fuel burning apparatus in which water is boiled to produce steam for space heating, power generation, or industrial processes. (more precisely) An apparatus in which a heat source other than a hot liquid or steam (most commonly burning fuel, exhaust gas from an internal combustion engine or gas turbine, waste heat from a process, solar energy or electricity) is used to boil water (or rarely another liquid), under pressure to provide steam (or other gas) for use as a heat source in calorifiers, heat exchangers or heat emitters, or for use directly for humidification, in an industrial process, or to power steam turbines. a kitchen vessel for steaming or boiling food
Geyser
Part of speech: noun
Definition: A boiling natural spring which throws forth at frequent intervals jets of water, mud etc., driven up by the expansive power of steam.An instantaneous, and often dangerous, hot water heater using hot steam.