The Collaborative International Dictionary of English v.0.48:

Distemper \Dis*tem"per\, v. t. [imp. & p. p. Distempered; p.
   pr. & vb. n. Distempering.] [OF. destemprer, destremper, to
   distemper, F. d['e]tremper to soak, soften, slake (lime);
   pref. des- (L. dis-) + OF. temprer, tremper, F. tremper, L.
   temperare to mingle in due proportion. See Temper, and cf.
   Destemprer.]
   1. To temper or mix unduly; to make disproportionate; to
      change the due proportions of. [Obs.]
      [1913 Webster]

            When . . . the humors in his body ben distempered.
                                                  --Chaucer.
      [1913 Webster]

   2. To derange the functions of, whether bodily, mental, or
      spiritual; to disorder; to disease. --Shak.
      [1913 Webster]

            The imagination, when completely distempered, is the
            most incurable of all disordered faculties.
                                                  --Buckminster.
      [1913 Webster]

   3. To deprive of temper or moderation; to disturb; to ruffle;
      to make disaffected, ill-humored, or malignant.
      "Distempered spirits." --Coleridge.
      [1913 Webster]

   4. To intoxicate. [R.]
      [1913 Webster]

            The courtiers reeling,
            And the duke himself, I dare not say distempered,
            But kind, and in his tottering chair carousing.
                                                  --Massinger.
      [1913 Webster]

   5. (Paint.) To mix (colors) in the way of distemper; as, to
      distemper colors with size. [R.]
      [1913 Webster]