There can be no such thing.
Since Malatesta terror has been a strategy used in the intimidation of governments and people.
It is our aspiration and our aim that everyone should become socially conscious and effective; but to achieve this end, it is necessary to provide all with the means of life and for development, and it is therefore necessary to destroy with violence, since one cannot do otherwise, the violence which denies these means to the workers.
Terror is used as means to an end. Device by which to show both your power and the weakness of governments. A device to raise awareness of your plight and to flock people to your banner. A means by which to show corruption and repression. A catalyst for widespread social disruption or a means to specific tactical end.
In the last two hundred years, across the world for an almost infinite number of political aims, terror has been used as an insurrectional strategy.
It is a path, a tool, a device, a method. It is not an end in itself.
There is no shared set of terrorist beliefs. There is no shared terrorist mentality. The anonymity of the practioner of terror is one of his/her strongest weapons.
To use the moniker 'Terrorist' is, I believe, to fall into a syntactical trap. A linguistic land mine set by hegemonic authority.
'Terrorist' is a term scarred with two centuries of association with 'evil'. From Robespierre, through the archetypal bomb-wielding wild-eyed anarchist and on into the era of international terrorism and the blinkered beardy fundamentalist, 'terrorist' conjures up a warehouse full of dangerous associations with anarchy, madness and brutality that can be wielded by authority like the medieval branding iron.
Terrorist is too big a word now. It subsumes meaning, swallows it whole and leaves only images and threats behind. Thus in using the word we become suckered into exactly the kind of non-thinking that authorities desire. In the popular imagination, terrorists become characters in themselves and their terror becomes its own end. We become blinkered to the root causes of such violence.
In branding as terrorist no further explanation is required as to their actions. They are terrorists therefore they carry out terrorism.
Terrorism always has an end. When a group is not readily given the label terrorists there intentions are readily known; Malcom X or the ANC or Striking miners who dropped fridges off flyovers all used terrorism to achieve ends far more well known than the acts they committed.
To call Hamas or Al Quieda or Sendero Luminoso freedom or resistance fighters is not to support them. This is blinkered ignorance. Freedom is not objective fact. It is a subjective state of being. And these people are fighting for what they see as freedom. That does not mean that one has to support them in this, especially when their conception of freedom runs contradictory to universal human rights and personal well-being. But at least it means there is some level of discourse surrounding the causes of such action.
If we assume they are terrorists, therefore they shall cause terror regardless, the position is self-deafeating and inevitably the only possible course of action is direct and violent opposition (we must have 90 days of detention and we must invade every threatening country because there is no alternative when dealing with terrorists - practioners of terror in the same way a dress-maker always makes dresses). Terrorists are terrorists because they are terrorists, and governments are never questionned, either for the causes or the consequences of the presence of such groups, and we quickly find ourselves goosestepping towards an unpleasant future.
We must defy such simplistic use of language.
When you say terrorist you are not calling a spade a spade, you are simply avoiding the issue of why the man is digging the whole in the first place.