Plain English Meaning
Small frozen raindrops that bounce when they hit the ground. They form when rain falls through a cold layer of air close to the surface and freezes on the way down.
Full Definition
Ice pellets are a form of precipitation consisting of small, transparent or translucent grains of ice, generally less than 5 mm in diameter, that form when raindrops fall through a layer of below-freezing air and freeze before reaching the ground. Their presence indicates a temperature inversion with warmer air aloft over a colder layer near the surface, and signals the likelihood of freezing rain at higher altitudes.