Noun tyranny has 2 senses
  1. dictatorship, absolutism, authoritarianism, Caesarism, despotism, monocracy, one-man rule, shogunate, Stalinism, totalitarianism, tyranny - a form of government in which the ruler is an absolute dictator (not restricted by a constitution or laws or opposition etc.)
    --1 is a kind of autocracy, autarchy
    --1 has particulars: police state
  2. absolutism, tyranny, despotism - dominance through threat of punishment and violence
    --2 is a kind of dominance, ascendance, ascendence, ascendancy, ascendency, control