Reflection is a central concept in education and training for pedagogical professions. In the scientific discourse, there are many different concepts that are not sufficiently explicated in empirical studies. This complicates the cross-study consideration of empirical findings. In this paper, we present a proposed definition that uses three core features (occasion-related mental process, explicit self-reference, and extended understanding of pedagogical practice) to provide a framework for the structured explication of specific studies’ understanding of reflection. The proposed definition can be systematically related to established models of reflection. A systematic review of 49 German-language empirical articles from the last 10 years shows that in a large number of empirical papers no explication of the understanding of reflection is provided. If they do, they often focus only on singular core features. Finally, it is discussed to what extent the proposed definition can contribute as a structuring aid to stimulate research and to make findings mutually referable to each other.