frost / frôst/ • n. a deposit of small white ice crystals formed on the ground or other surfaces when the temperature falls below freezing. ∎  a period of cold weather when such deposits form: when the hard frosts had set in. ∎ fig. a chilling or dispiriting quality, esp. one conveyed by a cold manner: there was a light frost of anger in Jack's tone. ∎  [in sing.] inf. , chiefly Brit. a failure.• v. [tr.] cover (something) with or as if with small ice crystals; freeze: each windowpane was frosted along its edges. ∎  [intr.] become covered with small ice crystals: a mustache that frosts up when he's ice-climbing. ∎  decorate (a cake, cupcake, or other baked item) with icing. ∎  tint hair strands to change the color of isolated strands. ∎  injure (a plant) by freezing weather. ∎ inf. anger or annoy: such discrimination frosted her no end.DERIVATIVES: frost·less adj.

frost In meteorology, atmospheric temperatures below 0°C (32°F) at the Earth's surface. The visible result of a frost is usually a deposit of minute ice crystals formed on exposed surfaces from dew and water vapour. In freezing weather, the ‘degree of frost’ indicates the number of degrees below freezing point. When white hoar-frost is formed, water vapour passes directly from its gaseous state to a solid, without becoming a liquid.

frost The condition in which the prevailing temperature is below the freezing point of water (0°C). This may lead to a deposit of ice crystals on objects (e.g. grass or trees). Such deposits result from condensation when the dew-point temperature is below freezing. See also black ice.

frost Condition in which the prevailing temperature is below the freezing point of water (0°C). This may lead to a deposit of ice crystals on objects, e.g. grass or trees. Such deposits result from condensation when the dew-point temperature is below freezing. See also BLACK ICE.

frost traditionally personified as Jack Frost (see Jack).
frost giants in Scandinavian mythology, the enemies of Thor.

See also so many mists in March, so many frosts in May.