English▸ noun a system for detecting the presence, direction, distance, and speed of aircraft, ships, and other objects, by sending out pulses of high-frequency electromagnetic waves that are reflected off the object back to the source.
▪ an apparatus used for radar.
▪ used to indicate that someone or something has or has not come to the attention of a person or group:
the band has been kind of off the radar these past few years.
– ORIGIN 1940s : from ra(dio) d(etection) a(nd) r(anging).