The Collaborative International Dictionary of English v.0.48:

Fortunate \For"tu*nate\ (?; 135), a. [L. fortunatus, p. p. of
   fortunare to make fortunate or prosperous, fr. fortuna. See
   Fortune, n.]
   1. Coming by good luck or favorable chance; bringing some
      good thing not foreseen as certain; presaging happiness;
      auspicious; as, a fortunate event; a fortunate concurrence
      of circumstances; a fortunate investment.
      [1913 Webster]

   2. Receiving same unforeseen or unexpected good, or some good
      which was not dependent on one's own skill or efforts;
      favored with good forune; lucky.

   Syn: Auspicious; lucky; prosperous; successful; favored;
        happy.

   Usage: Fortunate, Successful, Prosperous. A man is
          fortunate, when he is favored of fortune, and has
          unusual blessings fall to his lot; successful when he
          gains what he aims at; prosperous when he succeeds in
          those things which men commonly desire. One may be
          fortunate, in some cases, where he is not successful;
          he may be successful, but, if he has been mistaken in
          the value of what he has aimed at, he may for that
          reason fail to be prosperous.
          [1913 Webster]

WordNet (r) 3.0 (2006):

fortunate
    adj 1: having unexpected good fortune; "other, less fortunate,
           children died"; "a fortunate choice" [ant: unfortunate]
    2: supremely favored; "golden lads and girls all must / like
       chimney sweepers come to dust" [syn: fortunate, golden]
    3: presaging good fortune; "she made a fortunate decision to go
       to medical school"; "rosy predictions" [syn: fortunate,
       rosy]

Moby Thesaurus II by Grady Ward, 1.0:

56 Moby Thesaurus words for "fortunate":
   advantageous, appropriate, assured of success, auspicious,
   befitting, benign, benignant, blessed, blessed with luck, bright,
   coming, convenient, crowned with success, dexter, expedient, fair,
   favorable, favored, favoring, felicitous, fit, fitting, fortuitous,
   full of promise, golden, good, happy, in luck, lucky, lucky dog,
   made, man of substance, meet, of good omen, of happy portent,
   of promise, on the up-and-up, on top, opportune, out in front,
   promising, propitious, prosperous, providential, ripe, seasonable,
   sortable, succeeding, successful, suitable, surefire, timely,
   triumphant, well, well-timed, white