The Collaborative International Dictionary of English v.0.48:

Derange \De*range"\, v. t. [imp. & p. p. Deranged; p. pr. &
   vb. n. Deranging.] [F. d['e]ranger; pref. d['e]- = d['e]s-
   (L. dis) + ranger to range. See Range, and cf.
   Disarrange, Disrank.]
   1. To put out of place, order, or rank; to disturb the proper
      arrangement or order of; to throw into disorder,
      confusion, or embarrassment; to disorder; to disarrange;
      as, to derange the plans of a commander, or the affairs of
      a nation.
      [1913 Webster]

   2. To disturb in action or function, as a part or organ, or
      the whole of a machine or organism.
      [1913 Webster]

            A sudden fall deranges some of our internal parts.
                                                  --Blair.
      [1913 Webster]

   3. To disturb in the orderly or normal action of the
      intellect; to render insane.

   Syn: To disorder; disarrange; displace; unsettle; disturb;
        confuse; discompose; ruffle; disconcert.
        [1913 Webster]

WordNet (r) 3.0 (2006):

derange
    v 1: derange mentally, throw out of mental balance; make insane;
         "The death of his parents unbalanced him" [syn:
         unbalance, derange]
    2: throw into great confusion or disorder; "Fundamental
       Islamicists threaten to perturb the social order in Algeria
       and Egypt" [syn: perturb, derange, throw out of kilter]

Moby Thesaurus II by Grady Ward, 1.0:

54 Moby Thesaurus words for "derange":
   afflict, clutter, craze, debilitate, dement, devitalize, disable,
   disarrange, disarray, discommode, discompose, dishevel, dislocate,
   disorder, disorganize, distract, disturb, drive insane, drive mad,
   enervate, enfeeble, frenzy, hospitalize, incapacitate, incommode,
   inconvenience, indispose, invalid, lay up, litter, mad, madden,
   make mad, mess, mess up, misarrange, muss, muss up, perturb,
   reduce, ruffle, rummage, rumple, scatter, send mad, shatter,
   sicken, tousle, turn, unbalance, unhinge, unsettle, upset,
   weaken