Plain English Meaning

How far the small flap at the tail end of the airplane is tilted up or down from its level resting position when the pilot pulls or pushes on the controls. More tilt means more change in the nose's pitch.

Full Definition

The angular movement of the elevator, the hinged horizontal control surface at the tail of the airplane, away from its neutral (streamlined) position in response to fore-and-aft movement of the control yoke or stick. Pulling back deflects the elevator upward, which raises the nose; pushing forward deflects it downward, which lowers the nose. The amount of deflection is the size of that angular displacement.