Based on the Random House Dictionary, © Random House, Inc. 2012.
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| a children's mummer's parade, as on the Fourth of July, with prizes for the best costumes. |
| a printed punctuation mark (‽), available only in some typefaces, designed to combine the question mark (?) and the exclamation point (!), indicating a mixture of query and interjection, as after a rhetorical question. |
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hoarfrost  (hôr'frôst') Pronunciation Key
Frozen dew that forms a white coating on a surface. |
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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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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