Terrorism is a criminal act that influences an audience beyond the immediate victim. The United States Department of Defense defines terrorism as “the calculated use of unlawful violence or threat of unlawful violence to inculcate fear; intended to coerce or to intimidate governments or societies in the pursuit of goals that are generally political, religious, or ideological.” Within this definition, there are three key elements—violence, fear, and intimidation—and each element produces terror in its victims. The FBI uses this: "Terrorism is the unlawful use of force and violence against persons or property to intimidate or coerce a government, the civilian population, or any segment thereof, in furtherance of political or social objectives." The U.S. Department of State defines "terrorism" to be "premeditated politically-motivated violence perpetrated against non-combatant targets by sub-national groups or clandestine agents, usually intended to influence an audience.
The exasperating inability to define terrorism is betrayed in the vague terms of the UN’s Global Counter-Terrorism Strategy approved in 2006. It resolved to "strongly condemn terrorism in all its forms and manifestations, committed by whomever, wherever and for whatever purposes."