come back vs riposte

come back is not a noun while riposte is a noun.

Word	Noun	Adjective	Verb	Adverb
come back	No	No	Yes	No
riposte	Yes	No	Yes	No

As verbs, come back and riposte are synonyms defined as:

Other synonyms of come back include rejoin, repay, retort, return.

come back (noun)	riposte (noun)
	(fencing) a counterattack made immediately after successfully parrying the opponents lunge
	a quick reply to a question or remark (especially a witty or critical one)