/ Dictionary / Index P Platonic year: Meaning and Definition of Find definitions for: Platon'ic year' Pronunciation: [key] — Astron. Astron. a period of about 26,000 years, equal to the time required for a complete revolution of the equinoxes. Also calledCf. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Platonic solid Platonism Related Content Daily Word Quiz: spectral Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language