The authors analyze terrorism from the point of view of definitions in the national jurisdictions of the USA, China, EU, and Russia. They also compare approaches to determine key features of this phenomenon in the papers of the most cited researchers of terrorism. National counterterrorism policies are governed by national laws, which depend on the doctrinal basics of the definition of terrorism. The authors use such methods as content analysis and comparative analysis of legislations to identify important aspects of these doctrinal foundations for USA, China, EU, and Russia.