unutterable
/(ˌ)ʌnˈʌt(ə)ɹəbl̩/adj
High School
1
Not utterable; incapable of being physically spoken or voiced; unpronounceable.
2
Incapable of being articulated or expressed; indescribable, inexpressible.
3
Not allowed to be spoken; taboo, unspeakable.
4
Extremely bad or objectionable; unspeakable.