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.
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            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.
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            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.
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WordNet (r) 3.0 (2006):

tumultuously
    adv 1: in a tumultuous and riotous manner; "the crowd was
           demonstrating tumultuously" [syn: tumultuously,
           riotously]