Definitions are not only conceptual constructs, they emerge from practice, investigations and academic discourses what are embedded in history, institutional frames, political cultures and social realities. This observation makes even more sense when we discuss civil society, an interdisciplinary field whose demarcation change in time throughout theoretical debate in multiple disciplines and definitions assumes different contours in every country and social reality in which it operates. In this sense, we observe the importance of broadening definitions, in order to consider the plurality of types and ecologies of civil society world while. With this in mind, this chapter sets out to (re) discuss the definitions of civil society in social and political sciences. To this end, we begin by problematizing the classical conceptualizations of civil society, showing the similarities in the meanings historically attributed to this concept and highlighting a “positive” definition of civil society conceived more recently and its consequences, exploring the challenges on civil society definitions nowadays. Positivity here does not express a judgment in the sense of being “good” or “better” than others, but rather it centers on exploring the particularities of the phenomenon, defining it based on what civil society is and characterizing it, rather than solely by what it is not (negative) or how it complements or differs. Given this genealogy of the concept and the development of the debate on civil society, we argue to consider definitions and conceptualizations that are more open to the multiple organizational configurations, forms of action and patterns of social-state interactions that have been built up in civil societies historically and coexist in the fields of practice. With the trajectory, changes and challenges of this concept in mind we defend a research agenda that reinforces the coproduction of definitions for civil societies that are less normative and “modelling” and more experimental, capable of supporting investigations and empirical research that help advance the understanding of this complex, interdisciplinary and multifaceted phenomenon that is extremely relevant to strengthening democracy, social justice and sustainability.