cossack

A member or descendant of an originally (semi-)nomadic population of Eastern Europe and the adjacent parts of Asia, formed in part of runaways from neighbouring countries, that eventually settled in parts of the Polish-Lithuanian Commonweal

A member of a military unit (typically cavalry, originally recruited exclusively from the above).

A Ukrainian.

A mercenary, a violent thug: a regular or irregular soldier, police officer or security guard employed to persecute or oppress disfavoured groups, such as Jews or (striking) workers.

1865 The Coal and Iron Police are authorized by the Pennsylvania General Assembly to maintain order in the coal fields. The miners referred to these private policemen as "Cossacks" and "Yellow Dogs."

Southern and eastern European miners and other workers popularly referred to these hated troops as "Cossacks" because they acted like the similarly repressive troops used by the czar against workers in Russia during the Revolution of 1905 and on other occasions. "

Alternative letter-case form of Cossack.