The Collaborative International Dictionary of English v.0.48:

Disown \Dis*own"\, v. t. [imp. & p. p. Disowned; p. pr. & vb.
   n. Disowning.]
   1. To refuse to own or acknowledge as belonging to one's
      self; to disavow or deny, as connected with one's self
      personally; as, a parent can hardly disown his child; an
      author will sometimes disown his writings.
      [1913 Webster]

   2. To refuse to acknowledge or allow; to deny.
      [1913 Webster]

            Then they, who brother's better claim disown,
            Expel their parents, and usurp the throne. --Dryden.

   Syn: To disavow; disclaim; deny; abnegate; renounce;
        disallow.
        [1913 Webster]

WordNet (r) 3.0 (2006):

disown
    v 1: prevent deliberately (as by making a will) from inheriting
         [syn: disinherit, disown] [ant: bequeath, leave,
         will]
    2: cast off; "She renounced her husband"; "The parents
       repudiated their son" [syn: disown, renounce,
       repudiate]