Other forms: frosts
Frost is the thin white layer of ice that forms on cold clear nights. A heavy frost, frost on the grass, the first frost of the year.
Gardeners divide it carefully: a ground frost is on the surface, an air frost is measured above it, and the last frost date decides when tender plants go out. Frost also means the weather that causes it — three nights of frost. As a verb, to frost over is what a window does. Note frostbite, the injury; frosty, which describes both weather and an unfriendly greeting; and defrost.
1nounfrostA thin white layer of ice formed on cold nights.
“There was frost on the inside of the windows.”
2nounweatherWeather cold enough to freeze water.
“Three nights of frost finished the beans.”
frost is frozen moisture.
Old English forst is built from the same root as freeze, with the noun ending that also gives us words like harvest. The r and the o swapped places over time — the same metathesis that turned brid into bird.
Middle English
frost
English, today
frost
From Middle English frost. From Middle English frost, from an unmetathesized variant of Old English forst (“frost”), from Proto-Germanic frustaz (“frost”), from Proto-Indo-European prews- (“to freeze; frost”). Cognate with stq Froast, Fröäst (“frost”), West Frisian froast (“frost”), cim bròst, vrost, vròst (“frost”), Dutch vorst (“frost”), German Frost (“frost”), lb Frascht (“frost”), wym fröst (“frost”), Danish -, Faroese -, Icelandic -, Norwegian Bokmål -, Norwegian Nynorsk -, Swedish frost (“frost”), Latin pruīna (“hoarfrost, frost, rime, snow”). Related to freeze.
Etymology from Wiktionary, CC BY-SA