Plain English Meaning
Before you start your approach, you decide exactly what you'll do if you have to abandon the landing — full power, what pitch to hold, when to retract flaps and gear, and where you'll go. That way, if you actually need to go around, you're not figuring it out under pressure.
Full Definition
A go-around procedure that the pilot has mentally rehearsed and decided upon before beginning an approach, including the specific power setting, pitch attitude, configuration changes, and flight path to fly if the landing is rejected. It establishes the actions in advance so they can be executed and correctly when needed.