In America it is defined as:

activities that involve violent… or life-threatening acts… that are a violation of the criminal laws of the United States or of any State and… 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… [or]… (C) occur primarily outside the territorial jurisdiction of the United States…"
William Ayers gets the label of a terrorist but he was never convicted of 1 act of terrorism. He was apart of a RADICAL group weather underground. How does an individual get the label of a crime of which he was never convicted.