rime ice

The opaque and granular ice covering which forms on aircraft as it flies through clouds of supercooled liquid water. The rime forms due to a rapid freezing of small supercooled water drops as they touch the wings or other exposed surfaces. The drops freeze with pockets of air in between. If the supercooling is not as great and the supercooled drops are larger, the water will take longer to freeze and will from a transparent ice called glaze.