Plain English Meaning
An instrument approach where the path you fly down lines up closely enough with the runway that you can keep going straight to land, instead of circling around to line up.
Full Definition
An instrument approach procedure in which the final approach course is aligned within 30 degrees of the runway centerline, allowing the pilot to land straight ahead from the final approach segment without performing a circling maneuver. The descent is flown to published minimums identified as 'straight-in' (S-) on the approach chart.
Context Anchor
Seen on instrument approach charts and in instrument approach planning, especially when deciding whether a or other is required.