Plain English Meaning
Regular (non-military, non-water) airports on land that have lights so airplanes can find and use them at night. Their identifying beacon flashes white, then green, white, then green.
Full Definition
Civilian airports on land that are equipped with operational lighting for night use. On aeronautical charts and in the Chart Supplement, they are identified by a standard symbol and marked with a rotating beacon that alternates white and green flashes to identify the airport from the air at night.
Context Anchor
Seen in night flying and airport lighting discussions, especially when learning airport beacon color combinations.