The most commonly cited definition of industrial symbiosis (IS), by Chertow (2000), has served well to foster discussion and research for more than a decade. The definition reflected the state of research and practice at the time; as both have advanced, some terms have been interpreted in substantially different ways. In this article we analyze those generally used terms for their connection to the ecological metaphor that is the root of industrial ecology, and their varied interpretations in IS research and practice over time. We then propose an updated definition intended to communicate the essence of IS as a tool for innovative green growth: IS engages diverse organizations in a network to foster eco-innovation and long-term culture change. Creating and sharing knowledge through the network yields mutually profitable transactions for novel sourcing of required inputs and value-added destinations for non-product outputs, as well as improved business and technical processes. We posit that, although geographic proximity is often associated with IS, it is neither necessary nor sufficient—nor is a singular focus on physical resource exchange.