ultrasonic

adj.超声速的

ugliness, ugly, ugly-looking, UHF, UHT, UK, ukulele, ulcer, ulcerate, ulceration, ulcerous, ulna, ulterior, ultimate, ultimately, ultimatum, ultimo, ultra violet, ultra-, ultramarine, ultrasound, ultraviolet, ululate, ululation, Ulyanovsk, umber, umbilical, umbilical cord, umbilicus, umbra, umbrage, umbrella, umlaut, umpire, umpteen, umpteenth, un, un-, un-American, unabashed,