untouchable vs castaway

untouchable and castaway both are nouns.

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

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

Other hypernyms of untouchable include Ishmael, outcast, pariah.

untouchable (noun)	castaway (noun)
belongs to lowest social and ritual class in India	a shipwrecked person
	a person who is rejected (from society or home)

untouchable (adjective)	castaway (adjective)
forbidden to the touch
impossible to assail
beyond the reach of criticism or attack or impeachment
not capable of being obtained
(especially used in traditional Hindu belief of the lowest caste or castes) defiling