Member of any of several, formerly
horse-raising, Tatar groups of S and SW
Russia, the Ukraine, and Poland, who took in
escaped serfs, and lived in independent
communal settlements (military brotherhoods)
from the 15th to the 19th centuries. Later
they held land in return for military service
in the cavalry under Russian and Polish
rulers. After 1917, the various Cossack
communities were incorporated into the Soviet
administrative and collective system.