Terrorism is supposed to involve use of force or violence against **civilians**, not illegitimate governments.
Perhaps you could find the defintion of a terrorist organization in the Patriot act? The definition there is circular-- any organization that engages in terrorist activity which is not defined. However, domestic terrorism is defined as any act "dangerous to human life" that is a violation of the criminal laws of a state or the United States, if the act appears to be intended to: (i) intimidate or coerce a civilian population; (ii) 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. Hmmm... peaceful protest of an abortion clinic (trespassing) is clearly terrorism by this definition... in fact it is so broad it could mean almost anything... we get the government we deserve, by electing officials who don't even bother to read the bills they vote for.