U字开头的单词或词组
UNCuncorkunabatedundergradutiunstuckunhelpfulurinateunderworldupper-classuntouchedundisputedunisonupmostunusableunaidedunbindunrecordeduninterestedunrequitedunsophisticatedunsatisfactoryunemployment rateunchangeableunpreparedunsettlinguninhabitedunderlayunfruitfulUSAFunspeakableunoriginalulcerativeunfetteredunproductiveundeterminedupper lipunchangedupperclassmanunder the control ofunchartedupheaval