The unlawful use or threatened use of force or violence by a person or an organized group against people or property with the intention of intimidating or coercing societies or governments, often for ideological or political reasons.
the systematic use of violence as a means to intimidate or coerce societies or governments
unlawful, in reference to the first definition for terrorism
1. Not lawful; illegal.
2. Contrary to accepted morality or convention; illicit.
…
1: not conforming to legality, moral law, or social convention; “an irregular marriage”; “improper banking practices” [syn: improper, unconventional]
2: contrary to or prohibited by or defiant of law; “unlawful measures”; “unlawful money”; “unlawful hunters” [ant: lawful]
3: not morally right or permissible; “unlawful love”
4: having no legally established claim; “the wrongful heir to the throne” [syn: wrongful]
5: contrary to or forbidden by law; “an illegitimate seizure of power”; “illicit trade”; “an outlaw strike”; “unlawful measures” [syn: illegitimate, illicit, outlaw(a), outlawed]
For my own clarification spured on from a discussion with engel over the weekend.