U字開頭的單詞或詞組
umbilicalumpireunderstatementUFRunreliableunprecedenteduniformedutterlyundueuniformlyU.S.unpackingup thereURLunilaterallyubiquityunscrupulousunder attackutteranceunturnedundeniableupbringinguncheckedureaupper boundunluckilyUSSRup and downurethraundoubtedupendUPIunremarkableunderscoreuptimeunremarkedunfitunder discussionundressedun-UAunder arrest