Merriam-Webster Collegiate Dictionary - terror

 noun  Etymology: Middle English, from Anglo-French terrour, from Latin ~, from terrere to frighten; akin to Greek trein to be afraid, flee, tremein to tremble — more at tremble  Date: 14th century  1. a state of intense fear  2.  a. one that inspires fear ; scourge  b. a frightening aspect the ~s of invasion  c. a cause of anxiety ; worry  d. an appalling person or thing; especially brat  3. reign of ~  4. violent or destructive acts (as bombing) committed by groups in order to intimidate a population or government into granting their demands insurrection and revolutionary ~  Synonyms: see fear  • ~less adjective