Plain English Meaning

Weather conditions that can cause ice to build up on the airplane. You need two things at the same time: moisture you can see in the air, and air that is cold enough to freeze it.

Full Definition

Atmospheric conditions in which ice can form on an aircraft in flight. These conditions exist when visible moisture (such as clouds, rain, drizzle, snow, or fog with low visibility) is present and the outside air temperature is at or below freezing, typically considered +5°C or colder when droplets may be present.