sonar

sonar
    n 1: a measuring instrument that sends out an acoustic pulse in
         water and measures distances in terms of the time for the
         echo of the pulse to return; "sonar is an acronym for sound
         navigation ranging"; "asdic is an acronym for antisubmarine
         detection investigation committee" [syn: {sonar}, {echo
         sounder}, {asdic}]
    

30 Moby Thesaurus words for "sonar":
      astronavigation, bathometry, bathymetry, celestial navigation,
      chronometer, coastwise navigation, consolan, dead reckoning,
      depth sounding, echo sounding, echolocation, fathomage, fathoming,
      fix, line of position, loran, oceanography, pilotage,
      plane sailing, point-to-point navigation, radar, radio beacon,
      radio navigation, sextant, shoran, sofar, sounding, soundings,
      tables, water