This is the Slavic name for a country subdivision – what other countries call a “state” or a “province.” The former Soviet Union used the word, and it’s used by many former Soviet republics – Ukraine, Belarus, etc.
It literally translates from Russian as “region.”
There are 46 oblasts in current-day Russian. From Wikipedia:
The majority of oblasts are named after their administrative center, the official term for a capital city in an oblast, which is generally the largest city.
Not all of Russia is designated as in an oblast. For example, Sakha is the largest administrative area of Russia, and it’s known as a “republic.” There are 22 of those.
Republics are administrative divisions originally created as nation states to represent areas of non-Russian ethnicity. The indigenous ethnic group that gives its name to the republic is referred to as the titular nationality.
Why I Looked It Up
I had encountered the word often, and it has an interesting English “feel” to it – the appearance of “blast” makes it feel dramatic or violent, when it’s really pretty pedestrian.