Unutterable

improferibile

(incapable of being articulated or expressed — see also indescribable, inexpressible)

impronunciabile

(not utterable; incapable of being physically spoken or voiced — see also unpronounceable)

impronunciabile

(incapable of being articulated or expressed — see also indescribable, inexpressible)

indicibile

(incapable of being articulated or expressed — see also indescribable, inexpressible)

inenarrabile

(incapable of being articulated or expressed — see also indescribable, inexpressible)

infando

(incapable of being articulated or expressed — see also indescribable, inexpressible)

nefando

(extremely bad or objectionable — see also unspeakable)