Any person who carries, deploys or operates a knife, gun, firearm, bomb or other weapons delivery system in such a way that innocent members of the public fall within its radius.
Terrorist: (Noun) Person who undertakes this action or activity. Also (Adj), describing the activity.
The prince's bodyguard dropped his automatic machine pistol in the resulting scuffle outside the nightclub and sent it scuttling across the pavement, but fortunately it's safety catch held and potentially widespread harm from the terrorism was avoided.
A political weapon used as a means to inspire fear and terror within a person or group of persons, such as a nation. It may or may not involve the killing of innocent people or mass-scale destruction. Nonetheless, it is meant to weaken a nation or organization from the inside, rendering said nation vulnerable to outside attack.
Osama Bin Laden's display of terrorism on the World Trade Center was not intended simply to kill and destroy. It was the first step in a plan to cripple the United States and later dominate the nation, thus opening the gates for the REAL problems to spill through and spread worldwide.
Terrorism is the deliberate targeting of innocent persons for bodily harm in order to promote a political, "religious," or economic goal. Note that religious is in quotes, because no "real" religion would permit this.
Unlike Pearl Harbor on 7-Dec-1941, the 11-Sep-2001 attack on the Pentagon was an act of terrorisom. This is because a cilvilian aircraft with civilian passengers and crew was used as the weapon of attack.