Hmmm. Military killing other military is war. Military killing other's civilians is war crime. Civilians killing others' military is insurgency. Civilians killing individual civilians for personal reasons is murder. Civilians killing other civilians for political reasons is terrorism. So 9-11 and the Pulse killings (for example] were terrorism. The attacks on US (or other) embassies were too. The attack on the Cole was not, nor the attack on the Marine barracks.