1911 Encyclopædia Britannica/Sleet
SLEET (either from Nor. sletta, of the same meaning, or related to Ger. Schlosse, hailstone), that form of precipitation of water vapour condensed from the atmosphere, which reaches the ground in a partly frozen condition. Sleet may originate in the upper atmosphere either as rain, in which case, to become partly frozen, it must have fallen into a stratum of air colder than that in which it originated, or as snow, when the opposite must havetaken place, i.e. the snow in its descent must have encountered an air-temperature slightly above the freezing-point.