• synonyms


[pur-muh-frawst, -frost]
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  1. (in arctic or subarctic regions) perennially frozen subsoil.
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Origin of permafrost

First recorded in 1943; perma(nent) + frost
Also called pergelisol.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

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British Dictionary definitions for permafrost


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

C20: from perma (nent) + frost
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

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.

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Online Etymology Dictionary, © 2010 Douglas Harper

permafrost in Science


  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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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.