The Collaborative International Dictionary of English v.0.48:

Soothsayer \Sooth"say`er\, n.
   1. One who foretells events by the art of soothsaying; a
      prognosticator.
      [1913 Webster]

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

WordNet (r) 3.0 (2006):

soothsayer
    n 1: someone who makes predictions of the future (usually on the
         basis of special knowledge) [syn: forecaster,
         predictor, prognosticator, soothsayer]

Moby Thesaurus II by Grady Ward, 1.0:

33 Moby Thesaurus words for "soothsayer":
   Cassandra, Druid, astrologer, augur, calamity howler,
   crystal gazer, divinator, diviner, divineress, forecaster,
   foreknower, foreseer, foreshower, foreteller, fortuneteller,
   geomancer, haruspex, palmist, predictor, prefigurer, presager,
   prognosticator, prophesier, prophet, prophet of doom, prophetess,
   psychic, pythoness, religious prophets, seer, seeress, vates,
   weather prophet



Easton's 1897 Bible Dictionary:

Soothsayer
   one who pretends to prognosticate future events. Baalam is so
   called (Josh. 13:22; Heb. kosem, a "diviner," as rendered 1 Sam.
   6:2; rendered "prudent," Isa. 3:2). In Isa. 2:6 and Micah 5:12
   (Heb. yonenim, i.e., "diviners of the clouds") the word is used
   of the Chaldean diviners who studied the clouds. In Dan. 2:27;
   5:7 the word is the rendering of the Chaldee gazrin, i.e.,
   "deciders" or "determiners", here applied to Chaldean
   astrologers, "who, by casting nativities from the place of the
   stars at one's birth, and by various arts of computing and
   divining, foretold the fortunes and destinies of individuals.",
   Gesenius, Lex. Heb. (See SORCERER.)