SSR meaning in Governmental ?

The Republics of the Union of Soviet Socialist Republics or the Union Republics (Russian: Сою́зные Респу́блики, tr. Soyúznye Respúbliki) were ethnically based administrative units of the Union of Soviet Socialist Republics (USSR). The Soviet Union was created by the treaty between the soviet socialist republics of Belarus, Ukraine, Russia, and the Transcaucasian Federation, by which they became its constituent republics. For most of its history, the USSR was a highly centralized state despite its nominal structure as a federation of republics; the decentralization reforms during the era of Perestroika ("Restructuring") and Glasnost ("Openness") conducted by Mikhail Gorbachev are cited as one of the factors which led to the dissolution of the USSR in 1991.

There were two different types of republics in the Soviet Union: the larger union republics, representing the main ethnic groups of the Union and with the constitutional right to secede from it, and the smaller autonomous republics, located within the union republics and representing ethnic minorities.

The Karelo-Finnish Soviet Socialist Republic, a relic of the Soviet-Finnish War, became the only union republic to be deprived of its status in 1956. The decision to downgrade Karelia to an autonomous republic within the RSFSR was made unilaterally by the central government without consulting its population.