My colleague at the University of Utah College of Law, Amos Guiora, has just posted this very interesting paper on the appropriate definition of "terrorism." Here's the main point:

"The recommended definition captures the core elements of terrorism in clear and concise language. In reviewing scholarship and terrorists' writings, the overwhelming impression is that causing harm (physical or psychological) to the innocent civilian population is the central characteristic of terrorist action. The available literature articulates that harming civilians is the most effective manner from the terrorist mindset to effectuate their goals."

Guiora goes on to argue that, without a clear definition of terrorism, we won't take appropriate countermeasures. In particular, we need to understand that terrorism intends to disrupt daily life, and that effective counterterrorism measures will have to be based on that fact.