'The threat of violence and the use of fear to coerce, persuade, and gain public attention' (NACCJSG 1976)

'Political terrorism is the use, or threat of use, of violence by an individual or a group whether acting for or in opposition to established authority, when such action is designed to create extreme anxiety and/or fear-inducing effects in a target group larger than the immediate victims with the purpose of coercing that group into acceding to the political demands of the perpetrators.'
(Wardlaw 1982: 16)

'Premeditated, politically motivated violence perpetrated against non-combatant targets by sub-national groups or clandestine agents, usually intended to influence an audience.'
(US Department of State 2001: 13)

The one fundamental difference between the definition given by Wardlaw and that used by the US government in that the latter is concerned with sub-state actors, even if they may be supported by a state, whereas Wardlaw's definition embraces the actions of the state against its own population.

Williams, Paul D. Ed. Security Studies: An Introduction. pp.223-224/