Plain English Meaning
An instrument approach that tells you which direction to fly to line up with the runway, but does not give you a continuous glide path down to it. You manage the descent yourself using altitudes printed on the chart.
Full Definition
A standard instrument approach procedure that provides lateral guidance (course alignment to the runway) but does not provide vertical guidance meeting precision-approach standards. The pilot uses published step-down altitudes to descend toward a Minimum Descent Altitude (MDA), at which the runway environment must be in sight to continue.