The pre-eminent authority on the English language, the much-venerated Oxford English Dictionary, is disappointingly unobliging when it comes to providing edification on this subject, its interpretation at once too literal and too historical to be of much contemporary use:
Terrorism: A system of terror. 1. Government by intimidation as directed and carried out by the party in power in France during the revolution of 1789-94; the system of `Terror'. 2. gen. A policy intended to strike with terror those against whom it is adopted; the employment of methods of intimidation; the fact of terrorizing or condition of being terrorized.
These definitions are wholly unsatisfying. Rather than learning what terrorism is, one instead finds, in the first instance, a somewhat potted historical -- and, in respect of the modern accepted usage of the term, a uselessly anachronistic -- description. The second definition offered is only slightly more helpful. While accurately communicating the fear-inducing quality of terrorism, the definition is still so broad as to apply to almost any action that scares (`terrorizes') us. Though an integral part of `terrorism', this definition is still insufficient for the purpose of accurately defining the phenomenon that is today called `terrorism'.
A slightly more satisfying elucidation may be found in the OED's definition of the perpetrator of the act than in its efforts to come to grips with the act itself. In this respect, a `terrorist' is defined thus:
1. As a political term: a. Applied to the Jacobins and their agents and partisans in the French Revolution, esp. to those connected with the Revolutionary tribunals during the `Reign of Terror'. b. Any one who attempts to further his views by a system of coercive intimidation; spec. applied to members of one of the extreme revolutionary societies in Russia.
This is appreciably more helpful. First, it immediately introduces the reader to the notion of terrorism as a political concept. As will be seen, this key characteristic of terrorism is absolutely paramount to understanding its aims, motivations and purposes and critical in distinguishing it from other types of violence.