Plain English Meaning
A speed that is 40% faster than the slowest speed at which the airplane can still fly with the gear and flaps down for landing. It gives the pilot a safe cushion above stalling while turning toward the runway.
Full Definition
A target airspeed equal to 1.4 times the airplane's stalling speed in the landing configuration (gear down, full flaps, power off). Used as a recommended approach speed on the base leg of the traffic pattern, providing a margin above the stall while the airplane is configured for landing.
Context Anchor
You will see this in traffic pattern and landing discussions, especially when setting a safe speed on base leg before turning .