Purpose: Specific social and emotional learning (SEL) programs have been found to promote a myriad of positive outcomes, but definitions of the broader concept of SEL are varied in its practice and scholarly usage. It is unclear whether recent conceptual expansions of SEL to include Systemic and Transformative approaches shape the understanding of SEL among educational leaders. Communities of Practice (CPs) may serve as a dynamic knowledge source for revealing and shifting educator understanding of SEL. Thus, in the present study we asked: (1) How do educational leaders define SEL?; and (2) In what ways did definitions of SEL evolve over the course of CPs? Methods: We analyzed open-ended survey responses from educational leaders at county offices of education (N=46; 76% White, 65% women) at two time points. At Time 1, leaders defined SEL. After six monthly statewide SEL CPs, they were given the opportunity to update their definition. To analyze the data, we engaged in reflexive thematic analysis. Findings: At Time 1, educational leaders emphasized popularized competency-based SEL definitions, emphasized skills rather than systems, and described SEL as an individualistic rather than a civic intervention. At Time 2, many educational leaders shifted their definitions towards more systemic thinking and included more elements of equity. Implications: Exploring educational leaders' definitions of SEL, and any shifts, may inform approaches to building the capacity of educational leaders to provide SEL implementation support and using CPs for spreading and shaping the ideas of Systemic SEL and Transformative SEL.