Plain English Meaning
It's the speed you fly on final approach. You take the speed at which the airplane would stall with gear and flaps down, and multiply it by 1.3. That gives you a comfortable cushion above the stall as you come in to land.
Full Definition
A reference airspeed equal to 1.3 times the airplane's stalling speed in the landing configuration (gear and flaps extended, idle power). It is the standard target final approach speed used to ensure a safe margin above the stall while on approach to landing.
Context Anchor
Seen in descent, approach, and landing discussions when choosing a safe target speed before .