The Collaborative International Dictionary of English v.0.48:

Disorganize \Dis*or"gan*ize\, v. t. [imp. & p. p.
   Disorganized; p. pr. & vb. n. Disorganizing.] [Pref. dis-
   + organize: cf. F. d['e]sorganiser.]
   To destroy the organic structure or regular system of (a
   government, a society, a party, etc.); to break up (what is
   organized); to throw into utter disorder; to disarrange.
   [1913 Webster]

         Lyford . . . attempted to disorganize the church.
                                                  --Eliot
                                                  (1809).
   [1913 Webster]

WordNet (r) 3.0 (2006):

disorganize
    v 1: remove the organization from [syn: disorganize,
         disorganise] [ant: organise, organize]

Moby Thesaurus II by Grady Ward, 1.0:

99 Moby Thesaurus words for "disorganize":
   ablate, addle, addle the wits, atomize, ball up, becloud, bedazzle,
   befuddle, bewilder, bother, break up, bug, cloud, clutter,
   come apart, confuse, consume, corrode, crack up, crumble,
   crumble into dust, daze, dazzle, deactivate, debrief, decay,
   decompose, demob, demobilize, derange, detach, disarrange,
   disarray, disband, discharge, discombobulate, discomfit,
   discompose, disconcert, dishevel, disintegrate, disjoin, dislocate,
   dismiss, disorder, disorient, disperse, dissolve, disturb,
   embarrass, entangle, erode, fall to pieces, fission, flummox,
   flurry, fluster, flutter, fog, fuddle, fuss, go separate ways,
   jumble, knock galley-west, let go, litter, maze, mess, mess up,
   misarrange, mist, mix up, moider, molder, muddle, muss, muss up,
   muster out, part, part company, perplex, perturb, pother, put out,
   raise hell, rattle, release, ruffle, rumple, scatter, separate,
   split, split up, throw into confusion, tousle, unsettle, upset,
   waste away, wear away