Plain English Meaning

Something is plugging the small forward-facing tube that the airspeed indicator uses to sense the air rushing past the airplane. When that tube is blocked, the airspeed reading becomes unreliable and can fool the pilot.

Full Definition

A condition in which the pitot tube — the forward-facing tube that captures ram air pressure for the airspeed indicator — becomes obstructed by ice, insects, debris, or a left-on pitot cover, preventing accurate airspeed indication. Depending on whether only the pitot intake is blocked or both the intake and the drain hole are blocked, the airspeed indicator will respond incorrectly to changes in altitude and may read , , or remain stuck.