From Longman Dictionary of Contemporary Englishhoarfrosthoar‧frost /ˈhɔːfrɒst $ ˈhɔːrfrɒːst/ noun [uncountable] formal DNWEATHERa thin layer of ice that forms on objects outside when it is very cold SYN frost A light hoarfrost covered the fields.
Examples from the Corpus
hoarfrost• I open my eyes to a world clothed in the exquisite lace of hoarfrost.Origin hoarfrost (1200-1300) hoar “gray, white” ((11-20 centuries)) (from Old English har) + frost 