inexpressibly vs indescribably

inexpressibly and indescribably both are adverbs.

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

As adverbs, inexpressibly and indescribably are synonyms defined as:

Other synonyms of inexpressibly include ineffably, unspeakably, unutterably.

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