ETYM Old Eng. tirant, tiraunt, tyraunt, Old Fren. tiran, French tyran, Latin tyrannus, Greek tyrannos, originally, an absolute sovereign, but afterwards, a severe or cruel ruler.
A dictator or dictatorial person; SYN. autocrat, despot.
In the ancient Greek city-states, a usurper who seized power, especially in the 7th and 6th centuries bc. Tyrannies weakened aristocratic control, and could lead toward democracy. For example the Pisistratids at Athens and Polycrates in Samos were tyrants who actively promoted public building and civic culture while cultivating personal prestige and power.