ultrasound

n [U] sound withan ultrasonic frequency; ultrasonic waves 超声（波）: [attrib作定语] an ultrasound scan, eg to detect abnormality in a foetus 超声波扫描检查（如可用以检查胎儿是否畸形）.

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