(in arctic or subarctic regions) perennially frozen subsoil.
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
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British Dictionary definitions for permafrost
ground that is permanently frozen, often to great depths, the surface sometimes thawing in the summer
Word Origin for permafrost
C20: from perma (nent) + frost
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
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Word Origin and History for permafrost
1943, coined in English by Russian-born U.S. geologist Siemon W. Muller (1900-1970) from perm(anent) frost.
Online Etymology Dictionary, © 2010 Douglas Harper
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.
The American Heritage® Science Dictionary
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