ETYM Cf. Italian bloccata. Related to Block.
1. A war measure that isolates some area of importance to the enemy; SYN. encirclement.
2. Prevents access or progress.
Cutting-off of a place by hostile forces by land, sea, or air so as to prevent any movement to or fro, in order to compel a surrender without attack or to achieve some other political aim (for example, the Berlin blockade 1948).
During World War I Germany attempted to blockade Britain with intensive submarine warfare, and Britain attempted to blockade Germany. In 1990 a blockade by United Nations member countries was agreed in an attempt to force Iraq to withdraw from the invaded territory of Kuwait, but was superseded by open war.
No nation has the right to declare a blockade unless it has the power to enforce it, according to international law. The Declaration of London 1909 laid down that a blockade must not be extended beyond the coasts and ports belonging to or occupied by an enemy.

1. To impose a blockade on; SYN. seal off.
2. To obstruct access to; SYN. block off.