frost

A Dictionary of Aviation · 1911 · p. 10

fso:st x. 4. the act or state of freezing or becoming frozen; the temperature of the atmosfere when below the freezrng-point of water. black frost, frost net accompanied by hoar or rime: distinguisht from white frost. 2. frozen dew or vapor; hoar; rime; hoarfrost; white frost. 3