The Collaborative International Dictionary of English v.0.48:

Disorient \Dis*o"ri*ent\, v. t.
   1. To turn away from the east; to confuse as to which way is
      east; to cause to lose one's bearings. [R.] --Bp.
      Warburton.
      [1913 Webster]

   2. to cause (a person) to lose one's sense of direction; to
      cause to lose one's bearings or way; as, the tourist was
      disoriented by the winding and narrow streets.
      [PJC]

   3. (Psychiatry) to cause one to lose one's sense of time or
      place, or of one's own personal identity.
      [PJC]

   4. to confuse (a person) by changing or removing something
      which has served as a standard or guide to action; as,
      workers were rendered unemployed and disoriented by the
      rapid changes in the markets.
      [PJC]

WordNet (r) 3.0 (2006):

disorient
    v 1: cause to be lost or disoriented [syn: disorient,
         disorientate] [ant: orient, orientate]