What do we mean by "terrorist"?

Two things make me raise this issue for the umpteenth time.

First, there was a discussion on CNN the other day about the benefits and drawbacks of civil versus military courts in trying terror suspects. The success rates of civil courts was knocked by the CNN reporter who said it depended on how the word "terrorist" was being defined, as the court's definition included domestic terrorists, those involved in narco-terror, etc. and did not isolate Muslim terrorists. As though the successes of the courts in prosecution terrorists were a moot point without making such a differentiation. I, of course, began screaming at the T.V. (a common thing when I actually watch - my roommate likes to remind me the people behind the glass cannot hear me) that the courts obviously were defining terrorists as people who engage in acts that elicit terror, as opposed to Muslims who engage in acts that elicit terror. Quite a concept, no?

Second, and literally closer to home, today in Austin a man apparently burned down his home and then committed suicide by flying his small plane into an multi-story government office building. The latest news is that two bodies have been recovered, one the pilot and the other an IRS employee. His suicide note included a tirade against the IRS and U.S. government. Yet the local police are calling it a criminal act instead of a terrorist act. So, somebody with a grudge against the U.S. government flies a plane into a building, but it's not terrorism?

Or, as Sepia Mutiny notes, "Terrorist. For f*** sake!"

Does there have to be an organizational structure? What about more nebulous, cell-based groups with more tenuous direct linkages? Is the definition based on death tolls? What about a series of individual, isolated actions based on similar ideological beliefs? What about ETA, True IRA? Or are we just going for brown, funny name (Wait - Richard Reid? Eric Rudolph?), Muslim?
Peace/سلام