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"
having knowledge of; "he had no awareness of his mistakes"; "his sudden consciousness of the problem he faced"; "their intelligence and general knowingness was impressive"
state of elementary or undifferentiated consciousness; "the crash intruded on his awareness"