The Collaborative International Dictionary of English v.0.48:

Rehearsal \Re*hears"al\ (r?*h?rs"a), n.
   The act of rehearsing; recital; narration; repetition;
   specifically, a private recital, performance, or season of
   practice, in preparation for a public exhibition or exercise.
   --Chaucer.
   [1913 Webster]

         In rehearsal of our Lord's Prayer.       --Hooker.
   [1913 Webster]

         Here's marvelous convenient place for our rehearsal.
                                                  --Shak.
   [1913 Webster]

   Dress rehearsal (Theater), a private preparatory
      performance of a drama, opera, etc., in costume.
      [1913 Webster]

WordNet (r) 3.0 (2006):

dress rehearsal
    n 1: a full uninterrupted rehearsal in costumes shortly before
         the first performance