Plain English Meaning
It's the spot on an instrument approach where the pilot has to decide: either the runway is in sight and a safe landing is possible, or it's time to climb away and try again.
Full Definition
The Missed Approach Point is the position on an instrument approach procedure at which, if the required visual references for the intended runway are not in sight or a safe landing cannot be made, the pilot must execute the published missed approach procedure. Its location is depicted on the approach chart and is defined by a specific fix, distance, time from the final approach fix, or by reaching a published altitude (such as the on a ).