castaway vs misbeliever

castaway and misbeliever both are nouns.

Word	Noun	Adjective	Verb	Adverb
castaway	Yes	No	No	No
misbeliever	Yes	No	No	No

As nouns, misbeliever is a hyponym of castaway; that is, misbeliever is a word with a more specific, narrower meaning than castaway:

castaway: a person who is rejected (from society or home)
misbeliever: a person who holds religious beliefs in conflict with the dogma of the Roman Catholic Church

Other hyponyms of castaway include heretic, religious outcast, leper, Harijan, untouchable.

castaway (noun)	misbeliever (noun)
a shipwrecked person	a person who holds religious beliefs in conflict with the dogma of the Roman Catholic Church
a person who is rejected (from society or home)