An Etymological Dictionary of Astronomy and Astrophysics

1. The process or act of migrating; a migratory movement.
   

2. For an astronomical body, the process or act of changing its place over considerably large distances under the effect of certain physical forces. See, for example, → orbital migration; → Type I migration; → Type II migration.
   

3. Chem.: A movement or change of position of atoms within a molecule (Dictionary.com).

See also: → migrate; → -tion. Kuc “the act of moving from a dwelling, a place to another, decamping, migration.”