terror UK /ˈtɛɹə/US /ˈtɛɹɚ/noun 5adjective 1forms 3 noun5 •fear of the strongest kindThe terrors with which I was seized […] were extreme. — 1794 •Terrorism. •The action or quality of causing dread; terribleness, especially such qualities in narrative fiction. •Something or someone that causes such fear. •A night terror. adjective1 •(Philippines, slang) A strict teacher who fails most of the students.I have a terror math teacher. formsterrors · more terror · most terror