Real Dictionary

perestroika
uncountable noun: Perestroika is a term which was used to describe the changing political and social structure of the former Soviet Union during the late 1980s.

perestroika in American English
the policy of restructuring and reforming the economic, political, and social systems of the U.S.S. R. promoted by Mikhail Gorbachev beginning in the mid 1980s

perestroika in British English
noun: the policy of reconstructing the economy, etc, of the former Soviet Union under the leadership of Mikhail Gorbachov