Research on social cognition needs to overcome a disciplinary disintegration. On the one hand, in cognitive science and philosophy of mind – even in recent embodied approaches – the explanatory weight is still overly on individual capacities. In social science on the other hand, the investigation of the interaction process and interactional behaviour is not often brought to bear on individual aspects of social cognition. Not bringing these approaches together has unfairly limited the range of possible explanations of social understanding to the postulation of complicated internal mechanisms (contingency detection modules for instance). Starting from the question What is a social interaction? we propose a fresh look at the problem aimed at integrating individual cognition and the interaction process in order to arrive at more parsimonious explanations of social understanding. We show how an enactive framework can provide a way to do this, starting from the notions of autonomy, sense-making and coordination. We propose that not only each individual in a social encounter but also the interaction process itself has autonomy. Examples illustrate that these autonomies evolve throughout an encounter, and that collective as well as individual mechanisms are at play in all social interactions. We also introduce the notion of participatory sense-making in order to connect meaning-generation with coordination. This notion describes a spectrum of degrees of participation from the modulation of individual sense-making by coordination patterns, over orientation, to joint sense-making. Finally, we discuss implications for empirical research on social interaction, especially for studies of social contingency.