Gangs are commonly described as territorial groups of loosely affiliated youths that lack formal leadership and whose time in the gang is short. However, this narrow criterion ignores the protean nature of the gang construct. Street gangs, prison gangs, and outlaw motorcycle gangs possess similar and dissimilar characteristics, none of which are necessarily age–dependent. Moreover, gangs are dynamic groups whose motives, among other factors, have placed them on different trajectories. Some conform to conventional gang archetypes while others blur the lines between non–gang groups like cartels, terrorist organizations, and insurgents. Absent a unified definition, the referent object (gang) conforms to what Malcolm Klein quips as the “theoretician’s Rorschach,” where shifting boundaries of what constitutes a gang can lead to divergent reference points. Instead of a comprehensive gang definition, this chapter argues in favor of focusing on gang groupness for two prevailing reasons. One, the definitional debate relies on a fuzzy logic, where degrees of separation have been used to establish a set of definers and descriptors that fail to account for gang variability. Gangs have, at times, transformed into non–gang groups and vice versa. Second, just as gangs are dynamic, so too are the security implications of their activity. Taking the group as the unit of analysis provides an individualized approach to differentiate local from national threats. An important distinction to make when determining the appropriateness of anti–gang initiatives.