Source : Webster's Revised Unabridged Dictionary (1913)

Demesne \De*mesne"\, n. [OE. demeine, demain, rule, demesne, OF.
   demeine, demaine, demeigne, domaine, power, F. domaine
   domain, fr. L. dominium property, right of ownership, fr.
   dominus master, proprietor, owner. See {Dame}, and cf.
   {Demain}, {Domain}, {Danger}, {Dungeon}.] (Law)
   A lord's chief manor place, with that part of the lands
   belonging thereto which has not been granted out in tenancy;
   a house, and the land adjoining, kept for the proprietor's
   own use. [Written also {demain}.] --Wharton's Law Dict.
   Burrill.

   {Ancient demesne}. (Eng. Law) See under {Ancient}.

Source : WordNet®

demesne
     n 1: extensive landed property (especially in the country)
          retained by the owner for his own use; "the family owned
          a large estate on Long Island" [syn: {estate}, {land}, {landed
          estate}, {acres}]
     2: territory over which rule or control is exercised; "his
        domain extended into Europe"; "he made it the law of the
        land" [syn: {domain}, {land}]