The Collaborative International Dictionary of English v.0.48:

Self-defense \Self`-de*fense"\, n.
   The act of defending one's own person, property, or
   reputation.
   [1913 Webster]

   In self-defense (Law), in protection of self, -- it being
      permitted in law to a party on whom a grave wrong is
      attempted to resist the wrong, even at the peril of the
      life of the assailiant. --Wharton.
      [1913 Webster]