Plain English Meaning

Ice forming inside the engine's carburetor because the air cools sharply as it passes through. The ice blocks airflow, the engine loses power, and if it gets bad enough the engine can quit.

Full Definition

The formation of ice inside the carburetor of a piston aircraft engine, caused by the rapid temperature drop that occurs when fuel vaporizes and air accelerates through the carburetor venturi. The cooling effect can lower the internal temperature well below the outside air temperature, causing moisture in the air to freeze on the throttle valve and venturi walls. The accumulating ice restricts airflow, reducing engine power and, if untreated, can cause the engine to run rough or stop completely.