Terrorism has many definitions related to different and evolving national approaches to terrorism (Schmid, 2013).

The label ‘terrorist’ or ‘terrorism’ is regarded by countries as referring to unlawful violence but is also used to legitimize power or violence applied by these countries themselves.

The EU defines terrorist offences as ‘acts committed with the aim of seriously intimidating a population, unduly compelling a government or international organisation to perform or abstain from performing any act’, or ‘seriously destabilising or destroying the fundamental political, constitutional, economic or social structures of a country or an international organisation’.

The Dutch NCTV defines terrorism ‘as threatening, making preparations for or perpetrating, for ideological reasons, acts of serious violence directed at people or other acts intended to cause property damage that could spark social disruption, for the purpose of bringing about social change, creating a climate of fear among the general public, or influencing political decision-making’.

And the FBI defines terrorism as “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” (FBI, 2001).