Plain English Meaning
A radar-based air traffic control office that handles airplanes in the busy airspace around major airports — guiding them in for approach, lining them up for landing, and clearing them out after departure.
Full Definition
An air traffic control facility that uses radar and two-way radio to provide separation, sequencing, and approach services to aircraft arriving at, departing from, or transiting airspace surrounding one or more busy airports, typically out to about 30–50 nautical miles and up to around 10,000 feet. It sits between the tower (which handles the runway and immediate airport area) and the en route center (which handles high- ).