The Collaborative International Dictionary of English v.0.48:

Disunite \Dis`u*nite"\, v. t. [imp. & p. p. Disunited; p. pr.
   & vb. n. Disuniting.]
   1. To destroy the union of; to divide; to part; to sever; to
      disjoin; to sunder; to separate; as, to disunite particles
      of matter.
      [1913 Webster]

   2. To alienate in spirit; to break the concord of.
      [1913 Webster]

            Go on both in hand, O nations, never be disunited,
            be the praise . . . of all posterity! --Milton.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Disunite \Dis`u*nite"\, v. i.
   To part; to fall asunder; to become separated.
   [1913 Webster]

         The joints of the body politic do separate and
         disunite.                                --South.
   [1913 Webster]

WordNet (r) 3.0 (2006):

disunite
    v 1: part; cease or break association with; "She disassociated
         herself from the organization when she found out the
         identity of the president" [syn: disassociate,
         dissociate, divorce, disunite, disjoint]
    2: force, take, or pull apart; "He separated the fighting
       children"; "Moses parted the Red Sea" [syn: separate,
       disunite, divide, part]