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[hawr-frawst, -frost, hohr-] /ˈhɔrˌfrɔst, -ˌfrɒst, ˈhoʊr-/
frost (def 2).
1250-1300; Middle English hor-frost. See hoar, frost Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the web for hoarfrost
  • Continuous air movement over the canopy prevents hoarfrost on leaves.
  • Moose looks frosted in the midst of hoarfrost and snowy branches.
British Dictionary definitions for hoarfrost


a deposit of needle-like ice crystals formed on the ground by direct condensation at temperatures below freezing point Also called white frost
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
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Word Origin and History for hoarfrost

c.1300, hore-forst; see hoar + frost (n.).

Online Etymology Dictionary, © 2010 Douglas Harper
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hoarfrost in Science
Frozen dew that forms a white coating on a surface.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Encyclopedia Article for hoarfrost

deposit of ice crystals on objects exposed to the free air, such as grass blades, tree branches, or leaves. It is formed by direct condensation of water vapour to ice at temperatures below freezing and occurs when air is brought to its frost point by cooling. Hoarfrost is formed by a process analogous to that by which dew is formed on similar objects, except that, in the case of dew, the saturation point of the air mass is above freezing. The occurrence of temperatures below 0 C (32 F) is not enough to guarantee the formation of hoarfrost. Additionally, the air must be initially damp enough so that when cooled it reaches saturation, and any additional cooling will cause condensation to occur. In the absence of sufficient moisture, hoarfrost does not form, but the water in the tissues of plants may freeze, producing the condition known as black frost.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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