What is the meaning of Rejoin?

To join again; to unite after separation.

To come, or go, again into the presence of; to join the company of again.

To state in reply.

To answer to a reply.

To answer, as the defendant to the plaintiff's replication.

in US patent law To re-insert a patent claim, typically after allowance of a patent application, applied to patent claims that had been withdrawn from examination under a restriction requirement, based on rejoinder .

Source: wiktionary.org