(especially in czarist Russia) a person belonging to any of certain groups of Slavs living chiefly in the southern part of Russia in Europe and forming an elite corps of horsemen.
Origin
1590-1600; < Polishkozak or Ukrainiankozák, ultimately < a Turkic word taken to mean “adventurer, freebooter,” adopted as an ethnic name by Turkic tribal groups of the Eurasian steppes
British Dictionary definitions for Cossack
Cossack
/ˈkɒsæk/
noun
1.
(formerly) any of the free warrior-peasants of chiefly East Slavonic descent who lived in communes, esp in Ukraine, and served as cavalry under the tsars
adjective
2.
of, relating to, or characteristic of the Cossacks: a Cossack dance
Word Origin
C16: from Russian kazak vagabond, of Turkic origin
Word Origin and History for Cossack
n.
1590s, from Russian kozak, from Turkish kazak "adventurer, guerilla, nomad," from qaz "to wander." The same Turkic root is the source of the people-name Kazakh and the nation of Kazakhstan.