[1] : The Collaborative International Dictionary of English v.0.48

rejoinder \rejoin"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
see also:
rejoin reply 

[2] : The Collaborative International Dictionary of English v.0.48

rejoinder \rejoin"der\, v. i.
   to make a rejoinder. archaic
   1913 webster

[3] : WordNet (r) 2.0

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: retort, return, riposte, replication,
           comeback, counter
     2: law a pleading made by a defendant in response to the
        plaintiff's replication
see also:
retort return riposte replication comeback counter 

[4] : Moby Thesaurus II by Grady Ward, 1.0

48 moby thesaurus words for "rejoinder":
   acknowledgment, answer, answering, antiphon, back answer,
   back talk, backchat, comeback, confutation, contraremonstrance,
   counteraccusation, counterblast, countercharge, counterclaim,
   counterreply, counterstatement, defense, echo, evasive reply,
   reaction, ready reply, rebuttal, rebutter, receipt, refutation,
   repartee, replication, reply, repost, rescript, rescription,
   respond, respondence, response, responsion, responsory, retort,
   return, reverberation, riposte, short answer, snappy comeback,
   surrebuttal, surrebutter, surrejoinder, witty reply, witty retort,
   yes-and-no answer

[5] : Bouvier's Law Dictionary, Revised 6th Ed (1856)

rejoinder, pleadings. the name of the defendant's answer to the plaintiff's 
replication. 
     2. the general requisites of a rejoinder are, 1. it must be triable. 2. 
it must not be double, nor will several rejoinders be allowed to the same 
declaration. 3. it must be certain. 4. it must be direct and positive, and 
not merely by way of recital or argumentative. 5. it must not be repugnant 
or insensible. 6. it must be conformable to, and not depart from the plea. 
co. litt. 304; 6 com. dig. 185 archb. civ. pl. 278; u. s. dig, pleading, 
xiii. 

Rejoinder >> R Words
Rejoinder, definition of term: Rejoinder
rejoinder_pag1.html