English▸ noun [mass noun] a system for detecting the presence, direction, distance, and speed of aircraft, ships, and other objects, by sending out pulses of radio waves which are reflected off the object back to the source.
▪ [count noun] an apparatus used for radar.
▪ [count noun] a person's capacity for intuitive perception; a special sensitivity for factors, trends, etc.:
keep your radar tuned to changes at work.
▪ used to indicate that someone or something has or has not come to the attention of a person or group:
he's off the radar in the UK but in his country of birth he's a well-known figure.
– ORIGIN 1940s: from ra(dio) d(etection) a(nd) r(anging).