inexpressibly vs unutterably

inexpressibly and unutterably both are adverbs.

Word	Noun	Adjective	Verb	Adverb
inexpressibly	No	No	No	Yes
unutterably	No	No	No	Yes

As adverbs, inexpressibly and unutterably are synonyms defined as:

Other synonyms of inexpressibly include indescribably, ineffably, unspeakably.

inexpressibly (adverb)	unutterably (adverb)
to an inexpressible degree	to an inexpressible degree