The Collaborative International Dictionary of English v.0.48:

Ripost \Ri*post"\, Riposte \Ri*poste"\, n. [F. riposte.]
   1. In fencing, a return thrust after a parry.
      [1913 Webster]

   2. A quick and sharp refort; a repartee. --J. Morley.
      [1913 Webster]

WordNet (r) 3.0 (2006):

riposte
    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: (fencing) a counterattack made immediately after successfully
       parrying the opponents lunge
    v 1: make a return thrust; "his opponent riposted"
    2: answer back [syn: retort, come back, repay, return,
       riposte, rejoin]