Tell me again who is a terrorist really?

I knew who is a terrorist, a person who terrorizes innocent people to gain a purpose but lately this term is getting blurred. I mean let’s start with the term. We all know that Al-Qaeda is a terrorist organization and so are its variations and loose affiliates but now the Muslim brotherhood who were a few weeks ago ruling Egypt are labeled as terrorists by the Saudis and other royal Arabs and sometimes by their own people. The term is starting to get blurred since if you don’t agree with some governments on some issues they call you a terrorists and whatever name. But it is also a shame that Muslims and Arabs particularly as divided as ever and calling each other terrorists when it is convenient for them so that the world can rally behind them. So the good guys and bad guys are now being used interchangeably. Can we just agree on a common definition of a terrorist? I have defined it in the previous paragraph and I know what they are but the message that is being conveyed to the world is that when you are on the side of the civilized world even if you are going to kill your own people protesting peacefully you will be called a terrorist no matter what. It is all about geo politics and the U.S. being a champion of democracy irrespective of the outcome should support democracy and its values without getting hung up about who is against them because democracy takes time to take root and the cost is also greater in the short term but in the long term, the world will come to like what the U.S. have to offer in terms of freedom, equality and honesty. So start telling people who the actual terrorists are?