Veganism is an increasingly popular lifestyle within Western societies. However, there is no consistent definition of veganism across published research or used by vegan advocacy groups. This has implications for measurement and coherence of the research literature, and adds to public confusion of what veganism entails. This exploratory study used a community sample across three dietary groups (vegan = 309, omnivore = 216, vegetarian = 95) to assess ranked preferences for definitions of veganism used by vegan advocacy groups. Participants were also asked to explain their ranking order in an open-ended question. Across all three dietary groups, the United Kingdom (UK) Vegan Society definition was preferred. The majority of vegans selected the UK definition as their first preference, omnivores underwent five rounds of preference reallocation before the UK definition was selected, and vegetarians underwent four rounds before the UK definition was selected. A reflexive thematic analysis participants’ explanation of their rankings identified four themes: (1) Diet vs. lifestyle, (2) Absolutism, (3) Social justice, and (4) Animal justice. There was community consensus regarding the definition of veganism, qualitatively the reasons for this preference best align conceptually with the UK definition. Future research should consider using the UK definition of veganism to increase coherence within the field, and that strict definitions of veganism may exclude people from the label.