self-de·fense /ˌsɛlfdɪˈfɛn(t)s/
  自衛
  Self-de·fense n. The act of defending one's own person, property, or reputation.
  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.
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  self-defense
       n : the act of defending yourself [syn: self-defence, self-protection]