Copied from the link you provided, as defined by The Crown Prosecution Service.
“The Terrorism Act 2000 defines terrorism, both in and outside of the UK, as the use or threat of one or more of the actions listed below, and where they are designed to influence the government, or an international governmental organisation or to intimidate the public. The use or threat must also be for the purpose of advancing a political, religious, racial or ideological cause.
The specific actions included are:serious violence against a person; serious damage to property;
endangering a person's life (other than that of the person committing the action);
creating a serious risk to the health or safety of the public or a section of the public; and
action designed to seriously interfere with or seriously to disrupt an electronic system.
The use or threat of action, as set out above, which involves the use of firearms or explosives is terrorism regardless of whether or not the action is designed to influence the government or an international governmental organisation or to intimidate the public or a section of the public.”