Plain English Meaning
The round dial on a navigation instrument that shows compass directions in degrees, which the pilot turns to pick the course they want to fly.
Full Definition
The rotating compass-card face on a VOR or HSI Course Deviation Indicator, marked in 360 degrees, used to select and display the desired course to or from a navigation station.
Context Anchor
Seen when using a course deviation indicator during radio navigation, especially when selecting a course to or from a ground station.