permafrost

American  

[pur-muh-frawst, -frost] / ˈpɜr məˌfrɔst, -ˌfrɒst /

noun

1. (in Arctic or subarctic regions) perennially frozen subsoil.

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permafrost British  

/ ˈpɜːməˌfrɒst /

noun

1. ground that is permanently frozen, often to great depths, the surface sometimes thawing in the summer

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permafrost Scientific  

/ pûr′mə-frôst′ /

1. A layer of soil or bedrock that has been continuously frozen for at least two years and as long as tens of thousands of years. Permafrost can reach depths of up to 1,524 m (4,999 ft). It is found throughout most of the polar regions and underlies about one fifth of the Earth's land surface.

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Etymology

Origin of permafrost

First recorded in 1943; perma(nent) + frost

Explanation

Permafrost is ground that is frozen permanently. As you can imagine, permafrost is extremely cold. If you know that frost has many cold-related meanings and permanent means "always," then you should be able to figure out what permafrost is: ground that is permanently frozen. You won't be able to plant a garden in permafrost — or do much with it — since it’s so hard and cold. You won't find permafrost in warm climates or places that have distinct seasons. Permafrost only exists in areas where it's cold all the time, so the ground never thaws out.

Example Sentences

See Examples For:

permafrost

In contrast, regions with discontinuous or isolated permafrost sometimes experienced weathering-driven carbon uptake that exceeded 100 percent of river CO2 emissions.

From Science Daily ● Jun. 20, 2026

A study published in Nature suggests that thawing permafrost may have an unexpected effect on the carbon cycle.

From Science Daily ● Jun. 20, 2026

Shortly afterward, lawmakers amended the country's glacier protection law to relax restrictions on mining in areas of permafrost, despite fears the new law could endanger crucial water supplies.

From Barron's ● May 23, 2026

It also protected what's known as the periglacial environment, which includes things like permafrost - water trapped in frozen soil.

From BBC ● Apr. 10, 2026

There should be permafrost, a perpetually frozen subsurface.

From "Cosmos" by Carl Sagan