terrible vs unspeakable

terrible and unspeakable both are adjectives.

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

As adjectives, terrible and unspeakable are synonyms defined as:

Other synonyms of terrible include abominable, atrocious, awful, dreadful, painful.

terrible (adjective)	unspeakable (adjective)
causing fear or dread or terror	exceptionally bad or displeasing
extreme in degree or extent or amount or impact	defying expression or description
intensely or extremely bad or unpleasant in degree or quality	too sacred to be uttered
exceptionally bad or displeasing