An Etymological Dictionary of Astronomy and Astrophysics

1. In a → star cluster, coming across of two stars so closely that their → orbits alter by
   their mutual → gravitational attractions.
   

2. As regards an → asteroid or → comet, a situation when it crosses the Moon’s orbit and approaches the Earth with a risk of collision. See also → close approach, → encounter.

See also: → close; → encounter.