untellable vs unutterable

untellable and unutterable both are adjectives.

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

As adjectives, untellable and unutterable are synonyms defined as:

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

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