Plain English Meaning

The slowest speed the airplane can fly without stalling when the flaps are all the way up. With the flaps up, the wing needs more speed to keep producing enough lift, so this stall speed is faster than it would be with flaps down.

Full Definition

The minimum airspeed at which an airplane can maintain controlled flight in a specified configuration with the wing flaps fully retracted. It is higher than the stall speed with flaps extended, because retracted flaps produce less lift at a given angle of attack, requiring more airspeed to keep the wing flying.

Context Anchor

Seen in airplane handling discussions, performance data, and abnormal situations such as an asymmetric or split-flap condition.