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"

Moby Thesaurus II by Grady Ward, 1.0:

130 Moby Thesaurus words for "interlude":
   abeyance, act, afterpiece, anacrusis, bass passage, bit, bourdon,
   break, breath, breather, breathing place, breathing space,
   breathing spell, breathing time, bridge, burden, cadence, caesura,
   cease-fire, chaser, chorus, cigarette break, cocktail hour, coda,
   coffee break, curtain, curtain call, curtain raiser, day off,
   development, divertimento, divertissement, division, downtime,
   drop, enforced respite, epilogue, episode, exode, exodus,
   exposition, expository scene, figure, finale, folderol, gap,
   half time, half-time intermission, halt, happy hour,
   harmonic close, hesitation, hiatus, hoke act, holiday, idyll,
   interim, intermezzo, intermission, intermittence, interregnum,
   interruption, interval, introduction, introductory phrase, lacuna,
   lapse, layoff, letup, lull, meantime, meanwhile, measure, movement,
   musical phrase, musical sentence, number, off-time, ornament,
   parenthesis, part, passage, pause, period, phrase, plateau,
   point of repose, prologue, quiet spell, recess, refrain, relief,
   remission, resolution, respite, response, rest, resting point,
   ritornello, routine, scene, section, shtick, sketch, skit,
   song and dance, spell, stand-down, stand-up comedy act, stanza,
   statement, stay, stop, stoppage, strain, striptease, surcease,
   suspension, tailpiece, tea break, time off, time out, truce, turn,
   tutti, tutti passage, vacation, variation, verse, wait