Terrorist. It's a word that sends chills up the spines of most people. The term is pejorative. It is an insult of the highest degree. Calling someone's actions "terrorism" and the person a terrorist by extension, is as serious a charge that can be laid against someone in this day and age. It has the same connotation as "child molester" or "baby killer." A terrorist has done something that offends the conscience and whose intent is to terrorize, frighten, harass and otherwise molest innocent people.
The intent is usually key to calling someone a terrorist. A murderer certainly strikes fear into the hearts of his or her victims -- a serial killer may inflict these acts with the intent of causing fear and terror. However, serial killers do their horrible acts for selfish gratification. Almost without exception, a terrorist feels that he or she is working for some higher aim. Many people associate terrorists almost exclusively with religious fanaticism, but this is not an accurate picture. Terrorists do what they do from motivation which may be religious, political, a mix of the two, or neither. They may be environmental extremists, or motivated by extreme devotion to animal rights.
One of the perplexing things about a terrorist is that many people would agree with many of their aims in principle. Most people want religious freedom, honesty in politics, environmental accountability, ethical treatment for animals. All are laudable goals -- until innocent people are terrorized in the process of promoting the agenda.
Of course, to Americans, the terrorist attack of 11 September 2001, is the most visible definition of terrorism and what a terrorist is. However, in Northern Ireland, the scars from years of terrorism by the IRA and the Protestant paramilitary branches are still visible. What of the 2005 attack on the London Underground? Or decades of terrorist actions on both sides of the conflict in Israel and Palestine? Regardless of the cause, when that cause becomes violent, it is terrorism and its participants are terrorists. They strongly feel the ends justify their means.
A terrorist may be perfectly sincere in his or her beliefs. He or she may be convinced of the rightness of their actions. However, modern humanity agrees that actions calculated to produce terror, simply to make a point or further an agenda, constitute terrorism. A terrorist often does not think of himself as such. He may call himself a rebel, a freedom-fighter, a soldier of justice, etc. She might even be insulted that someone would think of her as a terrorist. But if he or she deliberately engages in actions designed to harm or kill innocent people, that destroy property, that rob blameless people of their right to a peaceful everyday existence, that person is a terrorist.