cast-off vs throwaway

cast-off is not a noun while throwaway is a noun.

Word	Noun	Adjective	Verb	Adverb
cast-off	No	Yes	No	No
throwaway	Yes	Yes	No	No

As adjectives, cast-off and throwaway are synonyms defined as:

Other synonyms of cast-off include discarded, thrown-away.

cast-off (noun)	throwaway (noun)
	an advertisement (usually printed on a page or in a leaflet) intended for wide distribution
	words spoken in a casual way with conscious under-emphasis
	(sometimes offensive) a homeless boy who has been abandoned and roams the streets

cast-off (adjective)	throwaway (adjective)
thrown away	intended to be thrown away after use
	thrown away