Circumgalactic refers to the region surrounding a galaxy. In astronomy and astrophysics, circumgalactic research focuses on studying the gas, dust, and other material that exists in the outskirts of galaxies. This includes the halo of gas surrounding galaxies, as well as the interactions between galaxies and their surrounding environment. Circumgalactic research is important for understanding the formation and evolution of galaxies, as well as the processes that drive star formation and regulate the growth of galaxies.