Geographical inits. until 1991 (4)
I believe the answer is:
ussr
(Other definitions for ussr that I've seen before include "Former association of communist republics" , "Country established in 1922 and dissolved in 1991, in short" , "Former federation of Russial and other states" , "In brief, former Soviet federation" , "Country established in1922 and dissolved in 1991, in short" .)