| Noun | 1. | sonar - 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"measuring device, measuring instrument, measuring system - instrument that shows the extent or amount or quantity or degree of something navigational instrument - an instrument used for navigating pinger - a pulse generator used for echo sounding in sonar pulse generator - a generator of single or multiple voltage pulses; usually adjustable for pulse rate |