sonar

 
Pronunciation: /ˈsəʊnɑː/

noun

[mass noun]
  • a system for the detection of objects under water by emitting sound pulses and detecting or measuring their return after being reflected: [as modifier]: a weak sonar signal
  • [count noun] an apparatus used in sonar: we reduced the sensitivity of our scanning sonars
  • the method of echolocation used in air or water by animals such as whales and bats: the fishing nets are detectable by dolphin sonar

Origin:

1940s: from so(und) na(vigation and) r(anging), on the pattern of radar