unspeakable vs sacred

unspeakable and sacred both are adjectives.

Word	Noun	Adjective	Verb	Adverb
unspeakable	No	Yes	No	No
sacred	No	Yes	No	No

unspeakable (adjective)	sacred (adjective)
exceptionally bad or displeasing	concerned with religion or religious purposes
defying expression or description	(often followed by `to') devoted exclusively to a single use or purpose or person
too sacred to be uttered	made or declared or believed to be holy; devoted to a deity or some religious ceremony or use
	worthy of respect or dedication
	worthy of religious veneration