Wiktionary
autonomous oblast
n. One of the administrative divisions of the former Soviet Union created for certain “smaller” nations and characterized by following features: they were given an autonomy within a (w: union republic) or, in the RSFSR, within a krai; had a status lower than an (w Autonomous republics of the Soviet Union autonomous republic); had a different (w: titulary nation) from that of their union republic/krai. Abbreviated as AO.
Wikipedia
Autonomous oblast