Hail is precipitation consisting of small balls or pieces of ice with a diameter ranging from 5 mm to greater than 50 mm falling either separately or agglomerated.
Transport Canada, TP 10643 -When in Doubt. Small and Large Aircraft - Aircraft Critical Surface Contamination Training for Aircrew and Groundcrew, Glossary 7th Ed., Ottawa, ON, Canada 2004, http://www.tc.gc.ca/eng/civilaviation/publications /tp10643-glossary-1116.htm, (Avn Sfty - Canad) {652}