Real Dictionary

Iron Curtain
proper noun: People referred to the border that separated the Soviet Union and the communist countries of Eastern Europe from the Western European countries as the Iron Curtain.

iron curtain in American English
a barrier of secrecy and censorship regarded as isolating the Soviet Union and other countries in its sphere
noun: a barrier to understanding and the exchange of information and ideas created by ideological, political, and military hostility of one country toward another, esp. such a barrier between the Soviet Union and its allies and other countries during the Cold W

Iron Curtain in British English
noun: (formerly) the guarded border between the countries of the Soviet bloc and the rest of Europe