Definition of Domestic Terrorism (via Wikipedia)
The statutory definition of domestic terrorism in the United States has changed many times over the years; also, it can be argued that acts of domestic terrorism have been occurring since long before any legal definition was set forth.
Under current United States law, set forth in the USA PATRIOT Act, acts of domestic terrorism are those which: "(A) involve acts dangerous to human life that are a violation of the criminal laws of the United States or of any State; (B) appear to be intended— (i) to intimidate or coerce a civilian population; (ii) to influence the policy of a government by intimidation or coercion; or (iii) to affect the conduct of a government by mass destruction, assassination, or kidnapping; and (C) occur primarily within the territorial jurisdiction of the United States."