unaccompanied

a.(音)无伴奏的

umbilical, umbilical cord, umbilicus, umbra, umbrage, umbrella, umlaut, umpire, umpteen, umpteenth, un, un-, un-American, unabashed, unabated, unable, unabridged, unacceptable, unacceptably, unaccommodating, unaccountable, unaccountably, unaccounted, unaccustomed, unacknowledged, unadopted, unadulterated, unaffected, unaffordable, unafraid, unaided, unalloyed, unalterable, unaltered, unambiguous, unanimity, unanimous, unanimously, unannounced, unanswerable,