The concept of adversarial legalism has been widely used by scholars of law, public administration, public policy, political science, sociology, and Law and Society, but the varying ways in which the concept has been employed raise concerns that it has become stretched to the point of incoherence. We argue that adversarial legalism entails both a style, an everyday practice of dispute resolution and policy making with distinct attributes, and a structure of governance that can be compared to other structures of authority. Untangling these aspects of adversarial legalism allows us to make sense of its different uses and identify future avenues of inquiry. Despite its wide application, we argue that adversarial legalism is in fact underutilized, especially in studies aimed at understanding consequences of judicialization, legalization, and juridification in the United States and abroad. Expected final online publication date for the Annual Review of Law and Social Science, Volume 16 is October 13, 2020. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.