riposte vs rejoin

riposte is a noun but rejoin is not a noun.

Word	Noun	Adjective	Verb	Adverb
riposte	Yes	No	Yes	No
rejoin	No	No	Yes	No

As verbs, riposte and rejoin are synonyms defined as:

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

riposte (noun)	rejoin (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)

riposte (verb)	rejoin (verb)
answer back	answer back
make a return thrust	join again