Plain English Meaning

The slowest speed the airplane can fly without stalling when it is set up to land — gear down, flaps down, and trimmed for landing. Below this speed, the wing stops producing enough lift to keep flying.

Full Definition

The calibrated stalling speed, or the minimum steady flight speed at which the airplane is controllable, with the landing gear extended, the wing flaps in the landing position, and the airplane in the configuration it would normally be in for landing. VS0 is published in the Pilot's Operating Handbook and is marked as the lower end of the white arc on the airspeed indicator.