1. A point on the celestial sphere through which pass the backward extensions of the trail of a meteor as observed at various locations, or the backward extensions of trails of a number of meteors traveling parallel to each other.

2. A point on the celestial sphere toward which the stars in a moving cluster appear to travel.

1. Pertaining to motion of particles or radiation along radii from a common point or a small region.

2. A point, region, substance, or entity from which particles or radiations are emitted.