The Collaborative International Dictionary of English v.0.48:

Overcome \O`ver*come"\, v. t. [imp. Overcame; p. p.
   Overcome; p. pr & vb. n. Overcoming.] [AS. ofercuman. See
   Over, Come, and cf. Supervene.]
   [1913 Webster]
   1. To get the better of; to surmount; to conquer; to subdue;
      as, to overcome enemies in battle.
      [1913 Webster]

            This wretched woman overcome
            Of anguish, rather than of crime, hath been.
                                                  --Spenser.
      [1913 Webster]

   2. To overflow; to surcharge. [Obs.] --J. Philips.
      [1913 Webster]

   3. To come or pass over; to spread over. [Obs.]
      [1913 Webster]

            And overcome us like a summer's cloud. --Shak.
      [1913 Webster]

   Syn: To conquer; subdue; vanquish; overpower; overthrow;
        overturn; defeat; crush; overbear; overwhelm; prostrate;
        beat; surmount. See Conquer.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Overcome \O`ver*come"\, v. i.
   To gain the superiority; to be victorious. --Rev. iii. 21.
   [1913 Webster]

WordNet (r) 3.0 (2006):

overcome
    v 1: win a victory over; "You must overcome all difficulties";
         "defeat your enemies"; "He overcame his shyness"; "He
         overcame his infirmity"; "Her anger got the better of her
         and she blew up" [syn: get the better of, overcome,
         defeat]
    2: get on top of; deal with successfully; "He overcame his
       shyness" [syn: overcome, get over, subdue, surmount,
       master]
    3: overcome, as with emotions or perceptual stimuli [syn:
       overwhelm, overpower, sweep over, whelm, overcome,
       overtake]
    4: overcome, usually through no fault or weakness of the person
       that is overcome; "Heart disease can get the best of us"
       [syn: get the best, have the best, overcome]

Moby Thesaurus II by Grady Ward, 1.0:

156 Moby Thesaurus words for "overcome":
   affected, all up with, beat, beaten, best, bested, better, blind,
   blind drunk, blotto, break, broken-down, brokenhearted, cap,
   confounded, conquer, crush, crushed, cut up, dash, dashed, deck,
   defeat, defeated, demoralize, demoralized, desolated, discomfited,
   done for, done in, down, drown, drub, exceed, excel, fallen, fixed,
   floor, floored, go one better, heart-stricken, heart-struck,
   heartbroken, helpless, hors de combat, hurdle, improve on,
   influenced, inundated, knock down, knock over, lambasted, lathered,
   lick, licked, master, moved, neurasthenic, on the skids, out,
   out cold, outdone, outlive, outweigh, overbalance, overbear,
   overborne, overexcited, overmaster, overmastered, overmatch,
   overmatched, overpass, overpower, overpowered, overridden, overset,
   overthrow, overthrown, overtop, overturn, overturned, overwhelm,
   overwhelmed, overwrought, panicked, paralyzed, passed out, perfect,
   predominate, preponderate, prevail, prevail over, prostrate,
   prostrated, psych out, put to rout, reduced to jelly, rise above,
   rout, routed, ruined, scattered, send flying, settled, shake,
   shaken, shot, shot to pieces, silence, silenced, skinned,
   skinned alive, speechless, stampeded, stiff, stoned, stricken,
   subdue, subdued, subjugate, suppress, surmount, surpass, throw,
   top, tower above, tower over, transcend, trimmed, trip, trip up,
   triumph, triumph over, trounced, trump, unbrace, under the table,
   undo, undone, unglued, unman, unmanned, unnerve, unnerved,
   unstring, unstrung, upset, vanquish, whelm, whelmed, whip, whipped,
   win, worst, worsted