Purpose - The lack of a standard definition and data sources makes it hard to compare findings and advance our knowledge in the business angel's domain. The purpose of this paper is to tackle this problem by presenting a proposal of a potential definition of business angels that it based on ten issues identified in 30 years of business angels' research. Design/methodology/approach - The paper reviews 24 studies on business angels and classifies definition inconsistencies found in ten different issues. Those differences are compared with methodological choices on sampling and with subsequent results. Findings - The authors observe a connection between definitional and sampling choices, and the results obtained. Inconsistent definitions can lead to results that are more than 400 times higher in terms of investment per project, for example. Research limitations/implications - The authors believe that the main implication of proposing a standard definition of business angles could help the academia in decreasing the great observed diversity which is actually leading to inconsistent and incomparable results that limit our understanding of this phenomenon. Originality/value - This paper differs from previous studies as it tackles the problem by identifying the definitional issues and presents a framework in order to build a consensus definition, rather than just comparing definitions.