a person exercising absolute power, esp. a ruler who has absolute, unrestricted control in a government without hereditary succession.

(in ancient Rome) a person invested with supreme authority during a crisis, the regular magistracy being subordinated to him until the crisis was met.

a person who authoritatively prescribes conduct, usage, etc.

a dictator of fashion.

a person who dictates, as to a secretary.

noun

absolutist , adviser , authoritarian , autocrat , boss , chief , commander , despot , disciplinarian , fascist , hitler , leader , magnate , mogul , oligarch , oppressor , ringleader , slavedriver , totalitarian , tycoon , tyrant , usurper , big brother , fhrer , man on horseback , strongman , martinet , anarch , autarch , bully , caudillo , commissar , czar , duce , junta , ruler , satrap , tsar