An Etymological Dictionary of Astronomy and Astrophysics

The inward spiraling of an orbiting → black hole toward a central → supermassive black hole (SMBH) as it radiates → gravitational wave. As a
result, the orbit decays, and the orbital period decreases, leading to the → merging of
both black holes as they get close enough. Once merged, the single hole goes through a stage called → ringdown.

See also: → in; → spiral.