Terrorism can be difficult to conceptualize as an organizational phenomenon. We argue that an organizational understanding of terrorism is enhanced if we understand that the collectivities that conduct terrorism can adopt any or all of the three forms of organizing: formal organization, network, and social movement. In short, organizational studies can contribute to the study of terrorism by articulating this polymorphic framework of forms. Using four illustrative cases drawn from a variety of geographic and ideological contexts (the Euskadi Ta Askatasuna (ETA), Liberation Tigers of Tamil Elam [LTTE], Hezbollah, and Al-Qaeda), we demonstrate the value of the polymorphic framework to avoid problems with traditional definitions of terrorism. In addition, the polymorphic framework can inspire further research about why and how terrorist groups shift from more or less fragmented networks, more or less formal organizations, and more or less embedded in social movements.