Source : Webster's Revised Unabridged Dictionary (1913)

Ouster \Oust"er\, n. [Prob. fr. the OF. infin. oster, used
   substantively. See {Oust}.]
   A putting out of possession; dispossession; ejection;
   disseizin.

         Ouster of the freehold is effected by abatement,
         intrusion, disseizin, discontinuance, or deforcement.
                                                  --Blackstone.

   {Ouster le main}. [Ouster + F. la main the hand, L. manus.]
      (Law) A delivery of lands out of the hands of a guardian,
      or out of the king's hands, or a judgement given for that
      purpose. --Blackstone.

Source : WordNet®

ouster
     n 1: a person who ousts or supplants someone else [syn: {ejector}]
     2: a wrongful dispossession
     3: the act of ejecting someone or forcing them out [syn: {ousting}]