This paper considers the under researched area relating to defining and conceptualising non-formal teacher professional development. It makes the case for adopting the general term grassroots professional development, specifically when this is self-directed activity led by educators. The article serves the purpose of being a position paper for this term and associated activities and continues by exploring three examples of grassroots professional development, specifically events organised by educators (TeachMeets, EdCamps and BrewEd). The history of each example is discussed, drawing on the limited body of published research literature, plus grey sources and personal experiences of the lead author. This paper is intended to provide a definitive start point for further research on the general topic of grassroots teacher professional development, and these examples in particular. The commonalties of each example are also considered, along with some criticisms and considerations for practitioners. In doing so this paper also proposes the next steps for research in this area, namely investigation of the effectiveness of grassroots professional development.