The Collaborative International Dictionary of English v.0.48:

Revelation \Rev`e*la"tion\, n. [F. r['e]v['e]lation, L.
   revelatio. See Reveal.]
   1. The act of revealing, disclosing, or discovering to others
      what was before unknown to them.
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   2. That which is revealed.
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   3. (Theol.)
      (a) The act of revealing divine truth.
      (b) That which is revealed by God to man; esp., the Bible.
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                By revelation he made known unto me the mystery,
                as I wrote afore in few words.    --Eph. iii. 3.
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   4. Specifically, the last book of the sacred canon,
      containing the prophecies of St. John; the Apocalypse or
      Book of Revelation or The Revelation of Saint John.
      [1913 Webster]

WordNet (r) 3.0 (2006):

Book of Revelation
    n 1: the last book of the New Testament; contains visionary
         descriptions of heaven and of conflicts between good and
         evil and of the end of the world; attributed to Saint John
         the Apostle [syn: Revelation, Revelation of Saint John
         the Divine, Apocalypse, Book of Revelation]