hoar frost

== English == === Alternative forms === hoarfrost, hoar-frost === Etymology === From Middle English hore frost, horfrost [and other forms], from hor (“grey; greyish-white”, adjective) (from Old English hār (“grey”), ultimately from Proto-Indo-European *(s)ḱeh₃- (“darkness; shadow”)) + frost (“cold spell, freezing weather, frost; hoar-frost; rime”) (from Old English frost, forst, ultimately from Proto-Indo-European *prustós (“frost”)). The English word is analysable as hoar (“greyish-white; white”, adjective) +‎ frost. === Pronunciation === (Received Pronunciation) IPA(key): /ˈhɔː fɹɒst/ (General American) IPA(key): /ˈhoɹ ˌfɹɑst/ === Noun === hoar frost (countable and uncountable, plural hoar frosts) Originally, any frozen dew forming a white deposit on exposed surfaces. Synonym: white frost Coordinate terms: dew, glaze, rime (specifically, meteorology) Water vapour which has undergone deposition or desublimation (“transformation directly into ice crystals without first turning into liquid water”) when the air is cold and moist to form a white deposit on exposed surfaces. ==== Usage notes ==== Hoar frost (sense 2) technically differs from rime, as the latter is formed by supercooled liquid water droplets freezing on surfaces. ==== Derived terms ==== ==== Related terms ==== ==== Translations ==== === References === === Further reading === frost on Wikipedia.Wikipedia