Plain English Meaning
A type of airport radar used by controllers near busy airports. It shows where aircraft are, how high they are, and where weather is, all on the same screen.
Full Definition
A specific model of terminal-area surveillance radar used by air traffic control facilities such as TRACONs to detect and track aircraft within roughly 60 nautical miles of an airport. The ASR-9 provides controllers with aircraft position, altitude (via the associated secondary radar), and weather information on a single display, and it serves as the tool for and separating aircraft in the .