The theorizing of literary horror is characterized by constant change, and as it evolves it provides more insightful models of interpretation. As David Hartwell, one of the key theorists in the field, states in "The Dark Descent: The Evolution of Horror" (2001), horror has reached that point of development where we can finally appreciate its achievements. In literary criticism, scholarships devoted to the horror genre began to appear as early as the 1920s. Since then critical thought has been dealing with disagreements regarding its definition. In particular, the theory of horror operates such terms as "dark fantasy", "mystery story", "horror story", "gothic story", "story about the supernatural" and others, and they are often used as synonyms. Consequently, there is a need to clarify the definition of horror and its collocations, at least in those studies which have a theoretical component as a key one. While the definition of horror is still a matter of discussion, there is a consensus view on the genre’s key distinctive feature: creating a certain mood throughout the textual tissue. Particularly, a famous literary scholar John Cuddon claims that horror "shocks", "frightens", "induces a feeling of repulsion or loathing" (The Penguin Dictionary of Literary Terms and Literary Theory, 2014). Douglas E. Winter concurs with this statement while affirming in his introduction to the anthology "Prime Evil" (1989) that horror is not only a genre but an emotion. Hence, it is critical to identify the ways in which the emotion of horror is constructed in composition, plot mechanics and characterization, as well as outline specific linguistic and stylistic features of horror texts. This paper deals with the theoretical aspects of horror as it aims to refine its attributive features within the interest of literary criticism. We analyzed a variety of definitions of horror across various disciplines, in diachrony and synchrony, and proposed a definition that can be appropriated in literary horror studies.