Definitions of rejoinder
a defendant's answer to a claimant's reply or replication (=an old-fashioned term used to describe a claimant's reply to a defendant's plea). The term is now largely out of official use in the US and the UK, but is sometimes used in other jurisdictions and in international law.
El Salvador's rejoinder is due on December 28, 2014.
an official reply to something such as a report, document, or other official publication
The Ministry of Finance issued a rejoinder following the report's publication.