Since the introduction of Morrison and Boyd's textbook in organic chemistry over 50 years ago, reaction mechanisms and mechanistic reasoning using the electron-pushing formalism (EPF) have become a mainstay of organic chemistry courses. In recent years there have even been several papers in this Journal and others detailing research on how students attend to various aspects of this formalism. However, there are no explicit articulations of a definition or framework in the chemical or science education research literature on mechanistic reasoning using EPF. Although practicing chemists intuitively know what constitutes mechanistic reasoning, this paper presents results of a nationwide study of organic chemistry faculty regarding their understanding and use of this technique. Although a consensus definition did not emerge from this research, there were several common features to them. These features suggest an activity that has a back-of-the-envelope quality meant to generate possible pathways based on established patterns of reactivity. Consistent with this view, the experts' focus for skills required to develop dexterity in this type of mechanistic reasoning was on applied ones rather than those that are more theoretical in nature. Finally, the principal uses of mechanistic reasoning using EPF, according to the respondents, are to explain and predict outcomes of chemical processes.