The Collaborative International Dictionary of English v.0.48:

Carnival \Car"ni*val\, n. [It. carnevale, prob. for older
   carnelevale, prop., the putting away of meat; fr. L. caro,
   carnis, flesh + levare to take away, lift up, fr. levis
   light.]
   1. A festival celebrated with merriment and revelry in Roman
      Gatholic countries during the week before Lent, esp. at
      Rome and Naples, during a few days (three to ten) before
      Lent, ending with Shrove Tuesday.
      [1913 Webster]

            The carnival at Venice is everywhere talked of.
                                                  --Addison.
      [1913 Webster]

   2. Any merrymaking, feasting, or masquerading, especially
      when overstepping the bounds of decorum; a time of riotous
      excess. --Tennyson.
      [1913 Webster]

            He saw the lean dogs beneath the wall
            Hold o'er the dead their carnival     --Byron.
      [1913 Webster]

WordNet (r) 3.0 (2006):

carnival
    n 1: a festival marked by merrymaking and processions
    2: a frenetic disorganized (and often comic) disturbance
       suggestive of a large public entertainment; "it was so funny
       it was a circus"; "the whole occasion had a carnival
       atmosphere" [syn: circus, carnival]
    3: a traveling show; having sideshows and rides and games of
       skill etc. [syn: carnival, fair, funfair]