between 1917 and 1991, a country in Europe and Asia, whose full name was the Union of Soviet Socialist Republics (the USSR). The Soviet Union was the largest country in the world and was made up of 15republics (=separate nations), the most important of which was Russia. It was formed after the Russian Revolution in 1917 as a Communist state, led byLenin. It was one of the most powerful countries in the world, and many people regarded it as the enemy of the US and western Europe during the Cold War. In the 1990s the Soviet Union began to break up as many of the republics got rid of their Communist governments and made themselves independent.
Definition from the Longman Dictionary of Contemporary English Advanced Learner's Dictionary.
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