a king or other ruler with absolute, unlimited power; autocrat.

any tyrant or oppressor.

History/Historical . an honorary title applied to a Byzantine emperor, afterward to members of his family, and later to Byzantine vassal rulers and governors.

noun

autocrat , hitler , monocrat , oppressor , slavedriver , tyrant , big brother , fhrer , man on horseback , strongman , totalitarian , dictator , martinet , anarch , autarch , authoritarian , czar , disciplinarian , monarch , rigorist , ruler , satrap , satrapy , tsar