DUO
DUOBINARY
DUODECENNIAL
DUODECILLION
DUODECILLIONS
DUODECIMAL
DUODECIMALLY
DUODECIMALS
DUODECIMO
DUODECIMOS
DUODENA
DUODENAL
DUODENARY
DUODENECTOMIES
DUODENECTOMY
DUODENITIS
DUODENITISES
DUODENUM
DUODENUMS
DUOLOG
DUOLOGS
DUOLOGUE
DUOLOGUES
DUOMI
DUOMO
DUOMOS
DUOPOLIES
DUOPOLISTIC
DUOPOLY
DUOPSONIES
DUOPSONY
DUOS
DUOTONE
DUOTONES

34 words start with DUO.