Meaning of RADAR in English
■ noun a system for detecting the presence, direction, and speed of aircraft, ships, etc., by sending out pulses of radio waves which are reflected off the object back to the source.
1940s: from ra(dio) d(etection) a(nd) r(anging) .
Concise Oxford English vocab. Сжатый оксфордский словарь английского языка. 2004