Plain English Meaning

Ice that builds up on the outside of the airplane while flying through cold, moist air. It changes the shape of the wings and other surfaces, which makes the airplane heavier and harder to fly.

Full Definition

The accumulation of ice on the external surfaces of an aircraft in flight, occurring when the aircraft passes through visible moisture (such as clouds, rain, or drizzle) at temperatures at or below freezing. Ice can form on the wings, tail, propeller, windshield, antennas, and other exposed surfaces, altering the airfoil shape, adding weight, increasing drag, and reducing .