indescribable vs unutterable

indescribable and unutterable both are adjectives.

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

As adjectives, indescribable and unutterable are synonyms defined as:

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

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