Definition of: precession of the equinoxes

Astron.
A slow rotary motion of the equinoctial points on the ecliptic from east to west, causing the time between successive equinoxes to be appreciably shorter than it would otherwise be: caused by the combined attractive forces of the moon, sun, and planets upon the equatorial protuberance of the earth and completing a full cycle in about 26,000 years, a period known as the Platonic or great year.