noun.Dew-drops which have undergone deposition and frozen into ice crystals to form a whitedeposit on an exposed surface, when the air is cold and moist.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
noun.
ice crystals forming a white deposit (especially on objects outside)
Word Usage
"I did have to look it up, not sure myself, but the explanation was simple really, frozen dew, but the word hoarfrost sounds much more mystical."