The Collaborative International Dictionary of English v.0.48:

Disinherit \Dis`in*her"it\, v. t. [imp. & p. p. Disinherited;
   p. pr. & vb. n. Disinheriting.] [Cf. Disherit,
   Disheir.]
   1. To cut off from an inheritance or from hereditary
      succession; to prevent, as an heir, from coming into
      possession of any property or right, which, by law or
      custom, would devolve on him in the course of descent.
      [1913 Webster]

            Of how fair a portion Adam disinherited his whole
            posterity!                            --South.
      [1913 Webster]

   2. To deprive of heritage; to dispossess.
      [1913 Webster]

            And disinherit Chaos, that reigns here. --Milton.
      [1913 Webster]

WordNet (r) 3.0 (2006):

disinherit
    v 1: prevent deliberately (as by making a will) from inheriting
         [syn: disinherit, disown] [ant: bequeath, leave,
         will]