With the wide application of Internet, the negative sides related to cyberspace become prominent, including cyberbullying. In such a sense, it is necessary to delimit and define cyberbullying as one important legal term for some relevant cybercrimes. Cyberbullying, in its different forms, is common among children and adolescents, and is facilitated by the increased use of technology. But there is no global legal definition and standard in this area. The authors consider it significant to take into account the international perspective of instrumentalization of law in respect of cyberbullying, which may lead to the formulation of such a definition. This article first explores the definitions, legal mechanisms and its relevant laws in the US, the EU and China to find out their similarities and differences. It is found that cyberbullying as a sign is socially-constituted, is interpreted differently in various jurisdictions, which indicates that the exploration of a sign should be located within and is intertwined with social, cultural and historical backgrounds. This research, as a case study, also provides useful implications for the understanding and interpretation of legal terms in a more general context. At the same time, cultures nowadays pervade one another, and so phenomena that were initially local may quickly and unexpectedly become global. This is the case of cyberbullying, initially associated with children and adolescents as perpetrators and victims, being now also practiced by adults who harass other adults.