A. J. Coady has written that the question of how to define terrorism is "irresolvable" because "its natural home is in polemical, ideological and propagandist contexts".Experts disagree about "whether terrorism is wrong by definition or just wrong as a matter of fact; they disagree about whether terrorism should be defined in terms of its aims, or its methods, or both, or neither; they disagree about whether states can perpetrate terrorism; they even disagree about the importance or otherwise of terror for a definition of terrorism." State terrorism
State terrorism refers to acts of terrorism conducted by a state against its own citizens or against another state. United Nations
In November 2004, a Secretary-General of the United Nations report described terrorism as any act "intended to cause death or serious bodily harm to civilians or non-combatants with the purpose of intimidating a population or compelling a government or an international organization to do or abstain from doing any act". The international community has been slow to formulate a universally agreed, legally binding definition of this crime. These difficulties arise from the fact that the term "terrorism" is politically and emotionally charged. In this regard, Angus Martyn, briefing the Australian parliament, stated,

The international community has never succeeded in developing an accepted comprehensive definition of terrorism. During the 1970s and 1980s, the United Nations attempts to define the term floundered mainly due to differences of opinion between various members about the use of violence in the context of conflicts over national liberation and self-determination.
For instance, some branches of the United States government refused to label members of the Provisional Irish Republican Army (IRA) as terrorists while the IRA was using methods against one of the United States closest allies (the United Kingdom) that the UK branded as terrorism. This was highlighted by the Quinn v. Robinson case.Media outlets who wish to convey impartiality may limit their usage of "terrorist" and "terrorism" because they are loosely defined, potentially controversial in nature, and subjective terms.The 2020 Nashville bombing revived a debate over the use of the word "terrorism", with critics saying it is quickly applied to attacks by Muslims but reluctantly if at all used by white Christian men, such as the Nashville bomber. History
Depending on how broadly the term is defined, the roots and practice of terrorism can be traced at least to the 1st century AD. According to the contemporary Jewish-Roman historian Josephus, after the Zealotry rebellion against Roman rule in Judea, when some prominent Jewish collaborators with Roman rule were killed, Judas of Galilee formed a small and more extreme offshoot of the Zealots, the Sicarii Zealots, in 6 AD. They were a smaller and more radical offshoot of the Zealots which was active in Judaea Province at the beginning of the 1st century AD, and they can be considered early terrorists, although this is disputed.