Plain English Meaning
The exact compass heading the chart tells you to fly as you line up with the runway on an instrument approach.
Full Definition
The published magnetic course, shown in degrees, that an aircraft must fly inbound to the runway during an instrument approach. On an approach chart, APP CRS appears in the header band along with other primary approach data such as the final approach fix altitude, runway information, and minimums.
Context Anchor
Seen in the briefing area of an instrument approach chart, where the pilot reviews the numbers before flying the approach.