A circumplanetary disk is a disk surrounding a planet analogous to a circumstellar disk around a star. These are theorized and plans are to attempt to detect them around extra-solar planets. They are presumed to exist in young systems and presumed to be the source of moons.
Saturn's rings can be classified as a circumplanetary disk of sorts, but the term was coined for disks around the time of a planet's formation, i.e., when its moons generally formed. Saturn's rings are thought possibly to be leftovers from such a disk, or possibly debris from moons, broken up by impact or tidal force.