Platonic year Meaning, Definition & Usage

  1. noun time required for one complete cycle of the precession of the equinoxes, about 25,800 years
    great year.

WordNet

Definitions
  1. (Astron.), a period of time determined by the revolution of the equinoxes, or the space of time in which the stars and constellations return to their former places in respect to the equinoxes; called also great year. This revolution, which is caused by the precession of the equinoxes, is accomplished in about 26,000 years. Barlow.

Webster 1913