unbelievable vs dumfounding

unbelievable and dumfounding both are adjectives.

Word	Noun	Adjective	Verb	Adverb
unbelievable	No	Yes	No	No
dumfounding	No	Yes	No	No

unbelievable (adjective)	dumfounding (adjective)
beyond belief or understanding	bewildering or striking dumb with wonder
having a probability too low to inspire belief