The Collaborative International Dictionary of English v.0.48:

Disheritance \Dis*her"it*ance\ (d[i^]s*h[e^]r"[i^]t*ans), n.
   [Cf. OF. desheritance.]
   The act of disinheriting or state of being disinherited;
   disinheritance. [Obs.] --Beau. & Fl.
   [1913 Webster]