Plain English Meaning

Ice that is part rough and milky and part smooth and glassy, formed at the same time on the aircraft. It picks up the worst features of both kinds of ice — it sticks well, it builds an uneven shape, and it is difficult to shed.

Full Definition

A form of structural icing that combines the characteristics of both rime ice and clear ice on the same surface. It forms when supercooled water droplets of varying sizes strike the aircraft and freeze in a way that produces both the rough, milky, opaque texture of rime and the smooth, glassy, transparent layers of clear ice. The result is an irregular, rough deposit that is harder to remove than either type alone and that disrupts airflow more severely than rime ice on its own.

Context Anchor

Seen in structural icing discussions, especially when flying in clouds or freezing precipitation where droplet sizes and freezing behavior are not all the same.