Just prior to the public launch of Contest 2 - UK's new counter-terrorism strategy - Home Secretary Jacqui Smith redefined terrorism in an interview on the BBC's Politics Show. From the included video:
What we do much more clearly in this [Contest 2] document is that we say: these are the shared values [of democracy, of tolerance, of human rights] to which we subscribe, incidentally terrorism is about killing people but is also about trying to undermine these shared values.
Fighting the ‘battle of ideas’ was introduced in the first Contest strategy. It is ironic that this government has demonstrated a lack of respect for these shared values. For instance, it has imposed restrictions on demonstrations and more recently threatened those taking photographies, including press photo-journalists. The government was found in breach by the European Court of Human Rights in its blanket and indiscriminate retention of DNA. This Home Secretary even ignored her own judges, and the law, by taking to Belmarsh prison suspects after they had been released on bail.
(Jacqui Smith also pointed out that as part of Contest 2, there are "60,000 people that we're now training up to respond to a terrorist threat, in everywhere from our shopping centres to our hotels". SpyBlog debunked this training claim in its analysis of Contest 2.)
The present legal definition of terrorism used in UK legal systems, found in section 1, Terrorism Act 2000, as amended by the Terrorism Act 2006 (Lord Carlile looked at the the definition of terrorism in a report he published in 2007):
(1) In this Act “terrorism” means the use or threat of action where— (a) the action falls within subsection (2), (b) the use or threat is designed to influence the government or an international governmental organisation or to intimidate the public or a section of the public, and (c) the use or threat is made for the purpose of advancing a political, religious or ideological cause.
(2) Action falls within this subsection if it— (a) involves serious violence against a person, (b) involves serious damage to property, (c) endangers a person’s life, other than that of the person committing the action, (d) creates a serious risk to the health or safety of the public or a section of the public, or (e) is designed seriously to interfere with or seriously to disrupt an electronic system.
(3) The use or threat of action falling within subsection (2) which involves the use of firearms or explosives is terrorism whether or not subsection (1)(b) is satisfied.
(4) In this section— (a) “action” includes action outside the United Kingdom, (b) a reference to any person or to property is a reference to any person, or to property, wherever situated, (c) a reference to the public includes a reference to the public of a country other than the United Kingdom, and (d) “the government” means the government of the United Kingdom, of a Part of the United Kingdom or of a country other than the United Kingdom.
(5) In this Act a reference to action taken for the purposes of terrorism includes a reference to action taken for the benefit of a proscribed organisation.
The definition of terrorism that has wide international agreement, according to Justice Chaskalson, is that of 'criminal acts committed with the intent to cause death or serious bodily injury [(i.e., excluding damage to property)] with the purpose of provoking terror in order to compel governments or international organisations to do or abstain doing any act'. The focus is on the act rather than on the actor, i.e., anyone performing an act of terrorism is a terrorist - be it an individual, an organisation or a state.
At one extreme we have a definition of terrorism limited to criminals causing serious bodily injuries and death, and at the other we have Jacqui Smith's interpretation that includes law-abiding individuals who do not share some system of values. Take your pick.