1) Cossack chief 2) Cossack chief, almost adamant 3) Cossack leader 4) Military rank of Ukraine 
Cossack chief; the word was also used for the heads of criminal gangs during the first decade following the October Revolution.
• (n.) A hetman, or chief of the Cossacks.
(from the article `hetman`) ...century); the hetman wielki (`great hetman`) was the chief of the armed forces and the commander in the field when the king was not present. In ...
At'a·man noun [ Russian ataman' : confer Pol. hetman , German hauptmann headman, chieftain. Confer Hetman .] A hetman, or chief of the Cossacks. 
Cossack senior officer.
the elected chief of a Cossack village or military force.