Plain English Meaning

The slowest speed the airplane can fly without stalling when it is set up to land — flaps down, gear down, throttle at idle. Fly slower than this and the wing stops producing enough lift to keep flying.

Full Definition

VS0 is the calibrated power-off stalling speed, or the minimum steady flight speed at which the aircraft remains controllable, in the landing configuration. The landing configuration means flaps fully extended, landing gear down (if retractable), and engine power at idle. VS0 is shown on the airspeed indicator as the lower end of the .