discarded vs throwaway

discarded is not a noun while throwaway is a noun.

Word	Noun	Adjective	Verb	Adverb
discarded	No	Yes	No	No
throwaway	Yes	Yes	No	No

As adjectives, discarded and throwaway are synonyms defined as:

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

discarded (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

discarded (adjective)	throwaway (adjective)
thrown away	intended to be thrown away after use
	thrown away