Literally "storm bird" in Russian. Short for Bronirovannyi Shturmovik(Armored Attack Aircraft: storm bird).

"Shturmovik" is a generic term for heavily-armored attack aircraft in Soviet service. The most famous of which is the legendary Ilyushin Il-2, a flying tank from WW2.

Although the Soviets pioneered the concept of armored anti-tank aircraft, Sturmovik development fizzled out for most of the cold war, when they focused on fast fighter-bombers like the MiG-27. Eventually, the concept was reborn when the Sukhoi Su-25 entered service in the 1980s.