Plain English Meaning
It is the spot on the approach where, if you cannot land, you stop trying to land and start flying the published go-around route instead.
Full Definition
A waypoint depicted on an instrument approach chart that defines the point at which the pilot must begin the published missed approach procedure if a landing cannot be made. On RNAV (GPS) approaches, it is shown on the plan view with a specific symbol and is the point where the GPS automatically sequences from approach guidance to missed approach guidance.
Context Anchor
Seen in the plan view of instrument approach charts, especially RNAV and GPS approaches.