Source : Webster's Revised Unabridged Dictionary (1913)

Castle-guard \Cas"tle-guard`\, n.
   1. The guard or defense of a castle.

   2. (O. Eng. Law) A tax or imposition an a dwelling within a
      certain distance of a castle, for the purpose of
      maintaining watch and ward in it; castle-ward.

   3. A feudal tenure, obliging the tenant to perform service
      within the realm, without limitation of time.