Haiduk or Hajduk (i. e. cowherd), a name bestowed on a body of irregular infantry in Hungary who kept up a guerilla warfare in the 16th century against the Turks; in 1605 a stretch of territory on the left bank of the Theiss was conferred upon them, together with a measure of local government and certain other privileges; but in 1876 their territory was incorporated in the county of Hajdu; the name was in later times applied to the Hungarian infantry and to noblemen's retainers.