religious outcast vs castaway

religious outcast and castaway both are nouns.

Word	Noun	Adjective	Verb	Adverb
religious outcast	Yes	No	No	No
castaway	Yes	No	No	No

As nouns, castaway is a hypernym of religious outcast; that is, castaway is a word with a broader meaning than religious outcast:

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

Other hypernyms of religious outcast include Ishmael, outcast, pariah.

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