unutterable vs untellable

unutterable and untellable both are adjectives.

Word	Noun	Adjective	Verb	Adverb
unutterable	No	Yes	No	No
untellable	No	Yes	No	No

As adjectives, unutterable and untellable are synonyms defined as:

Other synonyms of unutterable include indefinable, indescribable, ineffable, unspeakable.

unutterable (adjective)	untellable (adjective)
defying expression or description	defying expression or description
too sacred to be uttered
very difficult to pronounce correctly