Even though the traction towards a circular economy (CE) is on the rise, and the benefits a CE has across ecological, economic, and social frontiers have been undeniable, still, CE-related developments and its adoption have not been appealing. This study conducts a systematic literature review of the CE-related literature in line with the ‘umbrella framework’ to find the current state of the diffusion and diversification of CE concepts both in the academic context as well as in application. Using a thematic and content analysis of the sampled literature, the study (i) develops a comprehensive and inclusive CE definition and (ii) examines the level of diffusion of CE in the economy. The study concludes that, even though CE-related developments are positive and promising, it is still in the validity phase of the umbrella framework and recommends focusing more on the application-based intervention of the CE.