The Collaborative International Dictionary of English v.0.48:

Hereditament \Her`e*dit"a*ment\, n. [LL. hereditamentum. See
   Hereditable.] (Law)
   Any species of property that may be inherited; lands,
   tenements, anything corporeal or incorporeal, real, personal,
   or mixed, that may descend to an heir. --Blackstone.
   [1913 Webster]

   Note: A corporeal hereditament is visible and tangible; an
         incorporeal hereditament is not in itself visible or
         tangible, being an hereditary right, interest, or
         obligation, as duty to pay rent, or a right of way.
         [1913 Webster]

WordNet (r) 3.0 (2006):

hereditament
    n 1: any property (real or personal or mixed) that can be
         inherited