permafrost

American  

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

noun

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

---

permafrost British  

/ ˈpɜːməˌfrɒst /

noun

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

---

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.

---

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

"There is an overwhelming amount of firsthand documentation indicating that dam-building compounds the glacial melt and permafrost melt already underway from warming," Tikos added.

From Barron's ● Sep. 1, 2026

Melting glaciers and thawing permafrost can also destabilise mountain slopes, increasing the risk of landslides and other hazards.

From Barron's ● Aug. 29, 2026

Scientists for years have warned of melting ice and permafrost, which is centuries-old frozen soil, in the Himalayas due to climate change.

From BBC ● Aug. 27, 2026

"The logic is that with a warming planet, you will see shrinking glaciers, lots of snow melt. The permafrost that is partially holding some mountainsides together is warming and thawing and degrading."

From BBC ● Aug. 27, 2026

At last he found what he wanted: a firm rock deep-anchored in the permafrost He backed against it, tensing his legs and choosing his moment.

From "The Golden Compass" by Philip Pullman