: the isolation by a warring nation of an enemy area (as a harbor) by troops or warships to prevent passage of persons or supplies; broadly: a restrictive measure designed to obstruct the commerce and communications of an unfriendly nation
Act of war whereby one party blocks entry to or departure from an enemy area, often a coast. Blockades are regulated by international law and custom, which require advance warning to neutral states and impartial application. Penalties for breach of blockade are seizure of ship and cargo and their possible condemnation as lawful prizes. Neutral ships may not be destroyed for blockade running.