How do you define Terrorism?

What is really terrorism? This question must be simple to answer as it says that anytime somebody uses violence to gain something by hurting other people. But here is the catch, by this definition we can include many forms of activities which can fall under terrorism. Some people say that the drones above the heads of people targeting terrorists are also terrorizing the innocent population (you can read my take on drones in my previous posts). The gangs that target innocent people in their neighbors can also be called terrorists, and so are the criminals who mug, commit crime and harming people. Hacking into computers and taking money can be called financial terrorism in the sense that you are taking something which does not belong to yours or forcing yourself in places where you are not allowed. We can say that terrorism involves anything that cause undue fear in someone of somebody or coerce you into doing something which are not prepared to do in normal circumstances. And what about the collection agencies, when they call you and harass you (or terrorize you two different words with almost the same result) to pay your bills when you don’t have the money. What do we call them then? Although I know that most of the people would disagree with me but you have to think this thing through before blindly following some definition which can be very broadly applied. Right now the most common definition is anybody who puts fears in people who have nothing to do with it and uses violence to achieve their goals. But if you see the above situations, you will come to realize that there are many situations where you feel terrorized.