The phrase "rule of terror" is often used to describe a government or regime that rules through fear, intimidation, and violence. However, there are several other synonyms that can be used to describe such a rule. One of the most commonly used synonyms is "reign of terror," which highlights the totalitarian and oppressive nature of such a rule. Another synonym could be "tyranny," which refers to the cruel and unjust exercise of power by a single authority. In addition, "oppression," "dictatorship," and "authoritarianism" are other words often used to describe a rule of terror. Regardless of the term used, all these words represent the threat and danger posed by unchecked power in the hands of those in authority.