Plain English Meaning
The block of sky around a major airport where a special radar facility manages the flow of aircraft coming in to land and heading out after takeoff.
Full Definition
The controlled airspace surrounding a busy airport or group of airports where arriving and departing aircraft are sequenced, separated, and guided by a Terminal Radar Approach Control (TRACON) facility. It typically extends from the surface up to around 10,000 feet and outward roughly 30 to 50 miles from the primary airport, though the exact shape and dimensions vary by location.
Context Anchor
You will see this term in instrument flying when discussing approach control, radar services, arrivals, departures, and the handoff between airport- controllers and controllers.