(politics, history, usually with the) The Reign of Terror during the French Revolution.

(politics, history, usually with the) Any specific one of several historical reigns of terror.

(countable, uncountable) Intense dread, fright, or fear.

(uncountable) The action or quality of causing dread; terribleness, especially such qualities in narrative fiction.

(countable) Something or someone that causes such fear.

(uncountable) Terrorism.

(pathology, countable) A night terror.