The Collaborative International Dictionary of English v.0.48:

Rejoinder \Re*join"der\ (-d?r), n. [From F. rejoindre, inf., to
   join again. See Rejoin.]
   1. An answer to a reply; or, in general, an answer or reply.
      [1913 Webster]

   2. (Law) The defendant's answer to the plaintiff's
      replication.
      [1913 Webster]

   Syn: Reply; answer; replication. See Reply.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Rejoinder \Re*join"der\, v. i.
   To make a rejoinder. [Archaic]
   [1913 Webster]

WordNet (r) 3.0 (2006):

rejoinder
    n 1: a quick reply to a question or remark (especially a witty
         or critical one); "it brought a sharp rejoinder from the
         teacher" [syn: rejoinder, retort, return, riposte,
         replication, comeback, counter]
    2: (law) a pleading made by a defendant in response to the
       plaintiff's replication