The Collaborative International Dictionary of English v.0.48:

Prognosticate \Prog*nos"ti*cate\, v. t. [imp. & p. p.
   Prognosticated; p. pr. & vb. n. Prognosticating.] [See
   Prognostic.]
   To indicate as future; to foretell from signs or symptoms; to
   prophesy; to foreshow; to predict; as, to prognosticate evil.
   --Burke.
   [1913 Webster]

         I neither will nor can prognosticate
         To the young gaping heir his father's fate. --Dryden.
   [1913 Webster]

   Syn: To foreshow; foretoken; betoken; forebode; presage;
        predict; prophesy.
        [1913 Webster]

WordNet (r) 3.0 (2006):

prognosticate
    v 1: make a prediction about; tell in advance; "Call the outcome
         of an election" [syn: predict, foretell,
         prognosticate, call, forebode, anticipate,
         promise]
    2: indicate by signs; "These signs bode bad news" [syn: bode,
       portend, auspicate, prognosticate, omen, presage,
       betoken, foreshadow, augur, foretell, prefigure,
       forecast, predict]

Moby Thesaurus II by Grady Ward, 1.0:

43 Moby Thesaurus words for "prognosticate":
   adumbrate, announce, augur, bet, betoken, cast a horoscope,
   cast a nativity, divine, dope, dope out, dowse for water, forebode,
   forecast, foresee, foreshadow, foretell, foretoken, fortune-tell,
   gamble, guess, harbinger, hariolate, herald, make a prediction,
   make a prognosis, make a prophecy, make book, portend, predict,
   prefigure, presage, prophesy, read palms, read tea leaves,
   read the future, risk, signal, soothsay, speculate, take a chance,
   tell fortunes, tell the future, vaticinate