'Mare clausum' definitions:

Definition of 'mare clausum'

(from WordNet)
noun
(closed sea) a navigable body of water under the jurisdiction of a single nation

Definition of 'Mare clausum'

From: GCIDE
  • Mare clausum \Ma"re clau"sum\ [L.] (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. [Webster 1913 Suppl.]