Inexprimable.
ETYM Latin ineffabilis: cf. French ineffable. Related to In- not, and Effable, Fame.
Too sacred to be uttered; SYN. unnameable, unspeakable, unutterable.
Indescribable; unspeakable.
Defying expression; SYN. unexpressible.
ETYM Pref. un- not + speakable.
Not speakable; incapable of being uttered or adequately described; inexpressible; unutterable; ineffable.