In the absence of any agreed definition I thought the British Government's definition is as good as any:

"Terrorism" means the use or threat of action which involves serious violence against a person or serious damage to property; endangers a person's life, other than that of the person committing the action; creates a serious risk to the health or safety of the public or a section of the public; or is designed seriously to interfere with or seriously to disrupt an electronic system, where the use or threat is designed to influence the government or to intimidate the public or a section of the public, and the use or threat is made for the purpose of advancing a political, religious or ideological cause.

Also Merriam-Webster defines dissident as

disagreeing especially with an established religious or political system, organization, or belief