The Collaborative International Dictionary of English v.0.48:

Prophet \Proph"et\, n. [F. proph[`e]te, L. propheta, fr. Gr. ?,
   literally, one who speaks for another, especially, one who
   speaks for a god an interprets his will to man, fr. ? to say
   beforehand; ? for, before + ? to say or speak. See Fame. ]
   [1913 Webster]
   1. One who prophesies, or foretells events; a predicter; a
      foreteller.
      [1913 Webster]

   2. One inspired or instructed by God to speak in his name, or
      announce future events, as, Moses, Elijah, etc.
      [1913 Webster]

   3. An interpreter; a spokesman. [R.] --Ex. vii. 1.
      [1913 Webster]

   4. (Zool.) A mantis.
      [1913 Webster]

   School of the prophets (Anc. Jewish Hist.), a school or
      college in which young men were educated and trained for
      public teachers or members of the prophetic order. These
      students were called sons of the prophets.
      [1913 Webster]

WordNet (r) 3.0 (2006):

prophet
    n 1: an authoritative person who divines the future [syn:
         prophet, prophesier, oracle, seer, vaticinator]
    2: someone who speaks by divine inspiration; someone who is an
       interpreter of the will of God