ma·re clau·sum /ˈmɑr(ˌ)eˈklaʊsəm, ˈklɔ-/
  Ma·re clau·sum  Internat. Law Lit., closed sea; hence, a body of water within the separate jurisdiction of the nation; -- opposed to open sea (mare liberum), the water open to all nations and over which no single nation has special control.
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  mare clausum
       n : (closed sea) a navigable body of water under the
           jurisdiction of a single nation