: 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
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
Enabling next-generation geothermal and nuclear projects is great too. — Jordan Blum, Fortune, 11 Oct. 2026 Martinique has identified offshore wind and geothermal power as areas with significant potential, while a major program is equipping 67 schools with photovoltaic panels. — Panorama Media Ltd, Miami Herald, 9 Oct. 2026 Google is buying 115 megawatts of geothermal power in Nevada, and Meta has contracted for 150 megawatts from a geothermal plant in New Mexico. — Moones Alamooti, The Conversation, 9 Oct. 2026 Expanding the use of climate-friendly geothermal energy near places such as the Salton Sea and Sonoma and Modoc counties. — Los Angeles Times, 7 Oct. 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 14 Oct. 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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