From Wikipedia: "In the Roman Republic, the dictator (“one who dictates”), was an extraordinary magistrate (magistratus extraordinarius) with the absolute authority to perform tasks beyond the authority of the ordinary magistrate (magistratus ordinarius)"
The Roman Republic recognized that in times of crisis, decisive leadership was necessary. Not just in times of war or insurrection, but when the Republic had crucial business that needed to be attended to, the two consuls appointed by the Senate would defer their power to one dictator, who for a short period of time received absolute unquestioned authority to dispatched needed supplies and order necessary action without having to resort to the Senate or the people for approval.
For the business of the Republic, the dictator was appointed according to "execute and effect Roman State business denominated rei gerundae causa (for the matter to be done)"
These dictatorships could include supervising public works projects or resolving fiscal crises. It is in this second capacity that United States chief executives have resembled the ancient Roman dictator. In cutting spending and ruling out future outlays on behalf of the better interests of the state, they have received the most condemnation rather than in deference to the political machinations of the legislature or the popular interest of the voters.