Definition of radar noun from the Oxford Advanced Learner's Dictionary

 

radar

 noun
noun
BrE BrE//ˈreɪdɑː(r)//
 
; NAmE NAmE//ˈreɪdɑːr//
 
[uncountable] Plane travel, Parts of boats and ships
 
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  • a system that uses radio waves to find the position and movement of objects, for example planes and ships, when they cannot be seen They located the ship by radar. a radar screen compare sonar See related entries: Plane travel, Parts of boats and ships
  • Word Origin 1940s: from ra(dio) d(etection) a(nd) r(anging).Extra examples The aircraft suddenly went off the radar. The submarine is impossible to detect on radar. navigating by radar navigation by radarIdioms used to say that people are not aware of something Experts say a lot of corporate crime stays under the radar. The conflict has slipped below the radar of the mass media.
    on/off the radar screen
     
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    used to say that people’s attention is on or not on something The issue of terrorism is back on the radar screen. Since the scandal broke, all other issues seem to have disappeared off the radar screen as far as the media is concerned.
    See the Oxford Advanced American Dictionary entry: radar