Freezing rain is the name given to rain precipitation maintained at temperatures below freezing by the ambient air mass that causes freezing on contact with surfaces. Unlike sleet, a mixture of rain and snow, ice pellets, or hail, freezing rain is made entirely of liquid droplets. The raindrops become supercooled while passing through a sub-freezing layer of air hundreds of meters above the ground, and then freeze upon impact with any surface they encounter, including the ground, trees, electrical wires, aircraft, and automobiles. The resulting ice, called glaze ice, can accumulate to a thickness of several centimeters and cover all exposed surfaces. The METAR code for freezing rain is FZRA.

Source: https://en.m.wikipedia.org/wiki/Freezing_rain