A magistrate invested with absolute authority in ancient republican Rome in times of exigence and danger; the constitution obliged him to resign his authority at the end of six months, till which time he was free without challenge afterwards to do whatever the interest of the commonwealth seemed to him to require; the most famous dictators were Cincinnatus, Camillus, Sulla, and Caesar, who was the last to be invested with this power; the office ceased with the fall of the republic, or rather, was merged in the perpetual dictatorship of the emperor.