The Collaborative International Dictionary of English v.0.48:

Tumultuous \Tu*mul"tu*ous\ (t[-u]*m[u^]l"t[-u]*[u^]s), a. [L.
   tumultuosus: cf. F. tumultueux.]
   1. Full of tumult; characterized by tumult; disorderly;
      turbulent.
      [1913 Webster]

            The flight became wild and tumultuous. --Macaulay.
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   2. Conducted with disorder; noisy; confused; boisterous;
      disorderly; as, a tumultuous assembly or meeting.
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   3. Agitated, as with conflicting passions; disturbed.
      [1913 Webster]

            His dire attempt, which, nigh the birth
            Now rolling, boils in his tumultuous breast.
                                                  --Milton.
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   4. Turbulent; violent; as, a tumultuous speech.
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   Syn: Disorderly; irregular; noisy; confused; turbulent;
        violent; agitated; disturbed; boisterous; lawless;
        riotous; seditious.
        [1913 Webster] -- Tu*mul"tu*ous*ly, adv. --
        Tu*mul"tu*ous*ness, n.
        [1913 Webster]

WordNet (r) 3.0 (2006):

tumultuous
    adj 1: characterized by unrest or disorder or insubordination;
           "effects of the struggle will be violent and disruptive";
           "riotous times"; "these troubled areas"; "the tumultuous
           years of his administration"; "a turbulent and unruly
           childhood" [syn: disruptive, riotous, troubled,
           tumultuous, turbulent]

Moby Thesaurus II by Grady Ward, 1.0:

74 Moby Thesaurus words for "tumultuous":
   agitated, anarchic, angry, blaring, blatant, blatting, blustering,
   blusterous, blustery, boisterous, brassy, brawling, brazen,
   bullying, chaotic, clamant, clamorous, clamoursome, clanging,
   clangorous, clattery, disorderly, excited, fierce, frantic,
   frenzied, furious, hectic, hectoring, hellish, hysterical,
   infuriate, insensate, mad, mafficking, mindless, noiseful, noisy,
   obstreperous, orgasmic, orgastic, pandemoniac, rackety, raging,
   ranting, raucous, ravening, raving, riotous, rip-roaring,
   roistering, roisterous, rollicking, rowdy, rowdyish, rumbustious,
   savage, storming, stormy, strepitant, strepitous, swaggering,
   swashbuckling, swashing, tempestuous, termagant, troublous,
   turbulent, unrestrained, unruly, uproarious, violent, vociferous,
   wild