Tyranny is rule by a tyrant. A tyrant is a dictator who has far too much power and abuses power. Adolf Hitler, Joseph Stalin, Kim Jong II, Pol Pot and the Roman emperor Nero are just a few examples of tyrants. Tyrants are harsh and cruel and they care only about themselves and their ruling clique. Tyrants don’t care about ordinary people.
The word tyrant is also sometimes used to describe people who do not rule a whole country but who have too much power and use power oppressively. Heads of dysfunctional families or employers can become cruel tyrants.