The abbreviation EMRI for extreme mass ratio inspiral is used for orbits expected to inspiral yet have a mass ratio of 10,000 or greater, specifically, a supermassive black hole with a massive star or compact object orbiting it. They are proposed as a source of detectable gravitational waves and are some of the targets of planned space-based gravitational-wave detectors such as the LISA:
The orbital period and wave period would be in the range of hours. This circumstance was considered promising enough to contribute to the motivation for such space-based GW detectors, but there are factors which may make it too rare:
The term intermediate mass ratio inspiral (IMRI) is used for a similar circumstance surrounding a (theorized) intermediate-mass black hole, a possible target for ground detectors such as LIGO.