Definition
A radio detection device that provides information on range, azimuth, and/or elevation of objects by transmitting radio waves and analyzing the energy reflected back from those objects. This is the ICAO definition of radar as used internationally in air navigation services.
Plain English
Radar sends out radio waves, listens for the bounce back from objects like aircraft or weather, and uses that bounce to work out how far away the object is, what direction it is in, and sometimes how high it is.
Context Anchor
Pilots encounter radar in air traffic control services, weather avoidance, traffic displays, and discussions of how aircraft are tracked.
Derivation
Radar is a shortening of 'Radio Detection and Ranging.' The name itself describes the job: use radio waves to detect something and measure how far away it is. The [ICAO] tag means this is the wording adopted by the International Civil Aviation Organization for global use.
Why Pilots Care
Radar gives controllers the ability to separate traffic and issue vectors; pilots rely on onboard radar to detect and avoid hazardous weather.
Intuition Check
Radar does not mean only the screen a pilot or controller looks at. The screen is just the display; radar is the detection system that uses radio waves to find and track objects.
Example Sentence 1
Under ICAO procedures, the controller used radar to confirm the aircraft's range and azimuth before issuing a vector.
Example Sentence 2
The onboard weather radar painted a line of thunderstorms twenty miles ahead.