: of, relating to, or utilizing the heat of the earth's interior
also : produced or permeated by such heat
geothermal steam
geothermal regions

Did you know?

Geothermal comes partly from the Greek thermos, "hot". Most geothermal electricity is provided by power plants situated in areas where there is significant activity of the Earth's great tectonic plates—often the same areas where volcanoes are found. But hot water from deep underground may be used by cities far from volcanoes to heat buildings or sidewalks. And a newer source of geothermal energy relies on a less dramatic kind of heat: Individual homeowners can now install heat pumps that take advantage of the 50°-60° temperature of the soil near the surface to provide heating in cold weather (and air-conditioning in the warm months). These very small-scale geothermal systems may eventually supply more useful energy than the large power plants.

Examples of geothermal in a Sentence

Recent Examples on the Web
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The project is particularly relevant to New Mexico because XGS’ geothermal system is designed to operate without consuming water. — Neetika Walter, Interesting Engineering, 28 Sep. 2026 Operating as a bed and breakfast in recent years, the residence has undergone an impressive preservation campaign that added geothermal heating and cooling, updates to the electrical system, and upkeep of the wood finishes. — Richard Lane, Des Moines Register, 21 Sep. 2026 While renewable power can continue to expand, the energy sector is on the verge of leaps in cleaner, next-gen nuclear power and geothermal energy. — Jordan Blum, Fortune, 15 Sep. 2026 High-tech elements—motion-detectors, geothermal heat pumps, space-age insulation and the like—complement the old-school practices. — Condé Nast, Condé Nast Traveler, 11 Sep. 2026 See All Example Sentences for geothermal

Word History

Etymology

geo- + thermal entry 1

First Known Use

1875, in the meaning defined above

Time Traveler
The first known use of geothermal was in 1875

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Cite this Entry

“Geothermal.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/geothermal. Accessed 30 Sep. 2026.

Kids Definition

geothermal

adjective
variants also geothermic
-mik
: of, relating to, or using the heat of the earth's interior
also : produced by such heat
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