agnostic vs unbelieving

agnostic is a noun but unbelieving is not a noun.

Word	Noun	Adjective	Verb	Adverb
agnostic	Yes	Yes	No	No
unbelieving	No	Yes	No	No

agnostic (noun)	unbelieving (noun)
a person who claims that they cannot have true knowledge about the existence of God (but does not deny that God might exist)
someone who is doubtful or noncommittal about something

agnostic (adjective)	unbelieving (adjective)
uncertain of all claims to knowledge	holding that only material phenomena can be known and knowledge of spiritual matters or ultimate causes is impossible
of or pertaining to an agnostic or agnosticism	denying or questioning the tenets of especially a religion
	rejecting any belief in gods