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ˈhoar-frost
Formerly, and still often, two words.
[See hoar a. and frost n. 2.]
a. The white deposit formed by the freezing of dew, frozen dew, white frost. In scientific use now distinguished from rime.
Hoar-frost is a crystalline deposit of ice formed by the sublimation of water vapour; rime is a more amorphous deposit formed by the rapid freezing of supercooled droplets of water when they are brought by air currents into contact with a cold surface.
c1290St. Michael 617 in S. Eng. Leg. I. 317 Þe hore-forst [v.r. hor-forst] cometh ȝwane it is so cold þat it freoseth a-nyȝt, And þe Dev freose a-doneward. 1340Ayenb. 108 The zonne..wasteþ þe cloudes and þe hore urostes bi þe morȝen. 1535Coverdale Ps. cxlvii. 16 He geueth snowe like woll, & scatereth y⊇ horefrost like ashes. 1644Z. Boyd Gard. Zion 60 (Jam.) Sweet Mannah, round, small as the haire frost. 1730–46Thomson Autumn 1169 The rigid hoar-frost melts before his beam. 1880M. E. Braddon Just as I am xii, All the trees were fairy-trees wreathed with hoar-frost. 1895T. Russell Meteorol. iii. 53 Hoar-frost is a name given to the curious, regular figures resembling ferns that form on objects, especially on the window-panes in houses... Rime is a thick, heavy frost forming on objects from frozen rain or mist. 1921A. E. M. Geddes Meteorol. vi. 182 An examination of these crystals shows that they have not been deposited first as water drops, for they are not frozen drops of water. A deposit of this form is called hoar frost. 1967R. W. Fairbridge Encycl. Atmos. Sci. 402/1 ‘Frost’ has several meanings, most commonly implying hoar-frost or white frost which occurs when the air has been damp, leading to direct sublimation and the building of interlocking ice crystals on exposed surfaces.
fig.1852Badger Nestorians I. 243 The hoar⁓frost of care was prematurely sitting upon his locks.
attrib.1804A. Seward Mem. Darwin 323 A fine picture of an hoar-frost landscape.
b. hoar-frost curve or line: a line representing the conditions for equilibrium between the solid and the vapour phases of water in the absence of the liquid phase.
1879Encycl. Brit. VIII. 731/2 At this point the steam line, ice line, and hoar-frost line intersect, and it has therefore been called the triple point. 1940Glasstone Text-bk. Physical Chem. vi. 459 The vapor pressure curve of ice..is often called the hoar-frost curve.
Hence ˈhoar-frosty a.
1845Carlyle Cromwell (1871) I. 39 A cold hoarfrosty morning. |