an iron curtain an impenetrable barrier, especially the Iron Curtain, the physical and other barriers preventing the passage of people and information between the Soviet bloc and the West during the cold war.

☞ In the late 18th century, an iron curtain was literally a fire curtain in a theatre, but the figurative sense was in use from the early 19th century, well before Winston Churchill observed in a speech in March 1946 that 'an iron curtain has descended across the Continent [of Europe]'.