The Collaborative International Dictionary of English v.0.48:

Discompose \Dis`com*pose"\, v. t. [imp. & p. p. Discomposed;
   p. pr. & vb. n. Discomposing.] [Pref. dis- + compose: cf.
   OF. decomposer, F. d['e]composer.]
   1. To disarrange; to interfere with; to disturb; to disorder;
      to unsettle; to break up.
      [1913 Webster]

            Or discomposed the headdress of a prude. --Pope.
      [1913 Webster]

   2. To throw into disorder; to ruffle; to destroy the
      composure or equanimity; to agitate.
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            Opposition . . . discomposeth the mind's serenity.
                                                  --Glanvill.
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   3. To put out of place or service; to discharge; to displace.
      [Obs.] --Bacon.

   Syn: To disorder; derange; unsettle; disturb; disconcert;
        agitate; ruffle; fret; vex.
        [1913 Webster]

WordNet (r) 3.0 (2006):

discompose
    v 1: cause to lose one's composure [syn: upset, discompose,
         untune, disconcert, discomfit]