The Collaborative International Dictionary of English v.0.48:

Interlude \In`ter*lude\, n. [OE. enterlude, LL. interludium; LL.
   inter between + ludus play, fr. ludere to play: cf. F.
   interlude. See Ludicrous.]
   [1913 Webster]
   1. A short entertainment exhibited on the stage between the
      acts of a play, or between the play and the afterpiece, to
      relieve the tedium of waiting.
      [1913 Webster]

            Dreams are but interludes, which fancy makes
            When monarch reason sleeps.           --Dryden.
      [1913 Webster]

   2. A form of English drama or play, usually short, merry, and
      farcical, which succeeded the Moralities or Moral Plays in
      the transition to the romantic or Elizabethan drama.
      [1913 Webster]

   3. (Mus.) A short piece of instrumental music played between
      the parts of a song or cantata, or the acts of a drama;
      especially, in church music, a short passage played by the
      organist between the stanzas of a hymn, or in German
      chorals after each line.
      [1913 Webster]

   4. Hence: Any intervening period of time, space, etc.; a
      pause between phases of an activity.
      [PJC]

WordNet (r) 3.0 (2006):

interlude
    n 1: an intervening period or episode
    2: a brief show (music or dance etc) inserted between the
       sections of a longer performance [syn: interlude,
       intermezzo, entr'acte]
    v 1: perform an interlude; "The guitar player interluded with a
         beautiful improvisation"