Plain English Meaning
It is a set of markers on the ground at a small airport that shows pilots flying overhead which way the wind is blowing and which way to turn when entering the traffic pattern for each runway.
Full Definition
A ground-based visual aid located on or near a non-towered airport that gives arriving pilots key traffic pattern information at a glance. It typically consists of a central segmented circle surrounded by traffic pattern indicators showing the direction of turns for each runway, along with a wind direction indicator (such as a wind cone or tetrahedron) and, where installed, a landing direction indicator.
Context Anchor
Seen from the air when approaching an airport, especially an airport without an operating control tower.