To act as a tyrant; exercise tyrannical power; rule despotically or cruelly: used of persons, with over before an object.Hence To have a tyrannical influence; exercise oppressive restraint; maintain arbitrary control: used of things, commonly with over.To rule, treat, or affect tyrannically; act the tyrant to or over.To make tyrannically oppressive; convert into an instrument of tyranny.Also spelled tyrannise.