unutterable

adjectives

too sacred to be uttered
"the ineffable name of the Deity"
ineffable, unnameable, unspeakable, unutterable
defying expression or description
"indefinable yearnings"; "indescribable beauty"; "ineffable ecstasy"; "inexpressible anguish"; "unspeakable happiness"; "unutterable contempt"; "a thing of untellable splendor"
indefinable, indescribable, ineffable, unspeakable, untellable, unutterable
very difficult to pronounce correctly
"an unpronounceable foreign word"; "unutterable consonant clusters"
unpronounceable, unutterable