This article defines project business and employs a bibliometric study for considering the relevant characteristics of this concept. The motivation for this study is the shallow definition of project business in contemporary project studies. Furthermore, there is no overview on such relevant academic business sources that the project business concept would be built on. The research methodology utilises a bibliometric study of the most cited business journals. The bibliometric study results in key sources that can be considered as one scientific foundation for project business. However, this research goes beyond an ordinary bibliometric study, as the key sources were read and their content was carefully analysed. In this analysis, we constructed eleven article clusters, whilst simultaneously building up an understanding of the interrelatedness between articles and article clusters. The analysis results in seven findings that explore project business. The findings indicate that there is a need for several theoretical foundations: organisation theory, innovation theories, sociological and psychometric theories. Furthermore, in the future, there may be a need for a stronger body of strategy research. The analysis results in a definition of project business. According to this definition, the unit of analysis is a firm rather than a project. The firm and its business are in a focal role, whereas projects may be secondary. The findings, project business definition, and related reasoning contribute to new knowledge about the characteristics of project business. This knowledge is also relevant for further theory building and for developing novel managerial applications in business.