The word "terroist" is really in the eye of the beholder.
One example.
In WW2, the Danish resistance killed, assasinated, sabotaged, and blew up bombs against the Nazi occupation.
In Denmark they were celebreted, because they were freedom fighters, but the nazis (and the Danish government) called them terroists.
From Wiki:
The word "terrorism" is politically and emotionally charged, and this greatly compounds the difficulty of providing a precise definition. One 1988 study by the US Army found that over 100 definitions of the word "terrorism" have been used. A person who practices terrorism is a terrorist. The concept of terrorism is itself controversial because it is often used by states to delegitimize political opponents, and thus legitimize the state's own use of terror against those opponents.
And
The contemporary label of "terrorist" is highly pejorative; it is a badge which denotes a lack of legitimacy and morality. The application "terrorist" is therefore always deliberately disputed. Attempts at defining the concept invariably arouse debate because rival definitions may be employed with a view to including the actions of certain parties, and excluding others. Thus, each party might still subjectively claim a legitimate basis for employing violence in pursuit of their own political cause or aim.
http://en.wikipedia.org/wiki/Definition_of_terrorism
According to most of the definitions, Israel is doing terror against the Palastinian people, I hear no world leaders saying that.
When a state or governemnt think the word "terroism" is "appropriate" for their own gain, it's used.