unpronounceable(impossible or difficult to pronounce or articulate) adjective [UK: ˌʌn.prə.ˈnaʊn.səb.l̩] [US: ˌʌn.prə.ˈnaʊn.səb.l̩]This word is really unpronounceable. = Questa parola è davvero impronunciabile.
unutterable(not utterable; incapable of being physically spoken or voiced, see also: unpronounceable) adjective [UK: ʌn.ˈʌ.tə.rəb.l̩] [US: ʌn.ˈʌ.tə.rəb.l̩]