ter·ror 
(tĕrər)
(tĕrər)n.
1. Intense, overpowering fear. See Synonyms at fear.
2. One that instills intense fear: a rabid dog that became the terror of the neighborhood.
3. The ability to instill intense fear: the terror of jackboots pounding down the street.
4. Violence committed or threatened by a group, especially against civilians, in the pursuit of political goals.
5. Terror The Reign of Terror during the French Revolution.
6. Informal An annoying person or thing, especially an ill-mannered or disruptive child.
[Middle English terrour, from Old French terreur, from Latin terror, from terrēre, to frighten.]
Usage Note: The word terrorism is sometimes shortened to terror, especially in phrases like the war on terror. The difference between the two words is subtle. Dropping the -ism suffix changes the focus from a reprehensible method of conducting a violent conflict to a moral abstraction. Thus, the war on terror conjures a grave, universal conflict between good and evil, where the war on terrorism does not.