Introduction: the paper gives the analyses of the concept “terrorism” basing on the foreign and Russian scientific works. The purpose of the study is to review the definition “terrorism” in view of foreign and Russian scientific authors. The basic issues of the paper are confusion between terroristic and extremist activity, imbalance between regulatory framework and international rules. The relevance of the paper is defined by the danger of terrorism as a crime that threatens countries and citizens with its scale, direction, severity of consequences. These issues compel us to address its intrinsic character to find its origin. Materials and Methods: author used the following scientific methods: system, structular and functional, scientific and analytical, comparative analysis. Results: the genesis of the term «terror» is analyzed; on the basis of the international le-gal and domestic legislative framework, the legal characteristics of terrorism, developed at different times by legal scholars, have been systematized; positive developments of foreign criminal law are analyzed; the definition of «terrorism» is proposed. Discussion and Сonclusions: taking into account the specific features of terrorism, based on an analysis of the approaches to research into the phenomenon formulated in the scientific literature, the author proposes the following definition: terrorism is the ideological and physical methods of violent struggle, recognized as crimes related to encroachments on the life and health of persons, not related to the conflict, generating fear in an unlimited number of citizens for the purpose of influencing the bodies of state power, local self-government Or international organizations through the threat of undermining public security, the constitutional order and peace, and the security of mankind.