This paper sets out definitions of the entrepreneur, entrepreneurship and entrepreneurial activity for the purpose of supporting the development of related indicators. The paper recognises the long history in this area and the contention and differences that have existed, and that continue to exist, between academics who have confronted this issue over the last two centuries. It deliberately adopts a more pragmatic approach based on two principles ? relevance and measurability - resulting in definitions that are developed from both a bottom-up and top-down approach. Importantly, the definitions emphasise the dynamic nature of entrepreneurial activity and focus attention on action rather than intentions or supply/demand conditions. The paper concludes with an overview of policy implications arising from the definitions.