means a wintry mix of rain and partly frozen precipitation — ice pellets or snow melted into a cold, slushy mess that falls between rain and snow.

from From Middle English 'slete,' likely from an Old English root and related to similar words in other Germanic tongues — Middle High German 'slōz' (hailstone) and dialectal German 'Schlosse' are often cited as cousins. The deeper origin is uncertain, but the family seems to gather around the idea of small, hard, falling bits of ice.