Real Dictionary

rejoin
To rejoin means to answer quickly what someone has said, usually in a clever or critical manner.
verb: If you rejoin a group, club, or organization, you become a member of it again after not being a member for a period of time.
verb: If you rejoin a route, you go back to it after travelling along a different route for a time.
verb: If you rejoin someone, you go back to them after a short time away from them.

rejoin in American English 1
to answer
to say in answer
intransitive verb: to become joined together again
transitive verb: to come again into the company of

rejoin in American English 2
to become joined together again
to come into the company of again
intransitive verb: to answer; reply, esp. to counterreply
transitive verb: to say in answer; reply, esp. to counterreply

rejoin in British English 1
verb: to come again into company with (someone or something)

rejoin in British English 2
to say (something) in reply; answer, reply, or retort