Merriam-Webster Collegiate Dictionary - tyranny

 noun  (plural -nies)  Etymology: Middle English tyrannie, from Middle French, from Medieval Latin tyrannia, from Latin tyrannus tyrant  Date: 14th century  1. oppressive power every form of ~ over the mind of man — Thomas Jefferson; especially oppressive power exerted by government the ~ of a police state  2.  a. a government in which absolute power is vested in a single ruler; especially one characteristic of an ancient Greek city-state  b. the office, authority, and administration of a tyrant  3. a rigorous condition imposed by some outside agency or force living under the ~ of the clock — Dixon Wecter  4. a tyrannical act workers who had suffered tyrannies