define tyrant.
WordReference Random House Unabridged Dictionary of American English Â© 2016. tyâ¢rant (tÄ«â²rÉnt), n. 1  a sovereign or other ruler who uses power oppressively or unjustly. 2  any person in a position of authority who exercises power oppressively or despotically.  a tyrannical or compulsory influence.