Tyrant

TYRANT, government. The chief magistrate of the state, whether legitimate or otherwise, who violates the constitution to act arbitrarily contrary to justice. Toull. tit. prel. n. 32.
     2. The term tyrant and usurper, are sometimes used as synonymous, because usurpers are almost always tyrants; usurpation is itself a tyrannical act, but properly speaking, the words usurper and tyrant convey different ideas. A king may become a tyrant, although legitimate, when he acts despotically; while a usurper may cease to be a tyrant by governing according to the dictates of justice.
     3. This term is sometimes applied to persons in authority who violate the laws and act arbitrarily towards others. Vide Despotism.

A Law Dictionary, Adapted to the Constitution and Laws of the United States. By John Bouvier. Published 1856.