snowflakes that become rounded pellets due to riming; typical sizes are 2 to 5 millimeters in diameter (0.1 to 0.2 inch); graupel is sometimes mistaken for hail.
Found on https://www.encyclo.co.uk/local/10133
Small pellets of ice created when supercooled water droplets coat, or rime, a snowflake. The pellets are cloudy or white, not clear like sleet, and often are mistaken for hail. Found on http://www.encyclo.co.uk/local/22268