[pessimizer]

What terrorism is now (and for most of the 20th century) is an unbelievably politicized term that for around a decade was synonymous with Muslim who attacks anyone or advocates attacking anyone, including the soldiers occupying their countries. The term originated as a positive thing for late 19c anarchists who simply defined it as a tactic of asymmetric warfare against an enemy that so outnumbers you that they would be impossible to militarily defeat, so you break their morale through random, extremely varied attacks against individuals and small groups over an extended period of time, prioritizing as targets those who would normally feel the safest.

Terrorism isn't about "lawfulness." They just threw that in because violence and intimidation in the pursuit of political aims is what most countries do at all times. The definition wants to call war "lawful."