Scenario 1: Rebellion/Civil War
Rebellion against the lawful governing authority of a nation is not terrorism in and of itself. It is, however, a very interesting situation because the only thing that makes it legitimate is victory. Example - If the British had summarily stomped the holy living snot out of the colonies, then the leaders of the rebellion would all have most likely been hanged as traitors and the rebellion may not have been more than a footnote in the history of the British Empire. However, the colonies won and The British recognized the legitimacy of the new nation via The Treaty of Paris.
Now to apply this scenario to one of <interested individual> queries in which he asked "Are the Chechenians terrorists?". Those that are fighting the Russian soldiers and limiting their actions to those against soldiers or against infrastructure such as railroads aiding the soldiers movements I would say no, they are not terrorists. However, bombings in Moscow at movie theaters and the like..yes, that is a terrorist act.
It doesn't just apply to those fighting "against the system" either. It could be argued quite successfully that Sherman's march to the sea during the American Civil War was loaded with terrorist acts.