Mammoth Uncensored Word List:
53 - 4 letter words starting with u

udal udos ueys ufos ughs ugly ukes ules ulex ulna ulva umbo umph umps umpy unai unau unbe unce unci unco undo undy unit unix unto upas upby updo upgo upon upsy upta urao urde urds urdy urea ures urge uric urns urps ursa urus used user uses utis utus uvae uvas uvea