Meaning

noun a cruel and oppressive dictator

noun in ancient Greece, a ruler who had seized power without legal right to it

noun any person who exercises power in a cruel way

originFrom Middle English tyraunt, tiraunt, tyrant, tyrante, from Old French tyrant, from the addition of a terminal -t to tiran (cp. French tyran) via a back-formation related to the development of French present participles out of the Latin -ans form, from Latin tyrannus (“despot”), from Ancient Greek τύραννος (túrannos, “usurper, monarch, despot”), of uncertain origin.

Etymology from Wiktionary, CC BY-SA 3.0