/ Dictionary / Index P Plato: Meaning and Definition of Find definitions for: Pla•to Pronunciation: (plā'tō), [key] — n. 427–347b.c.,Greek philosopher. a walled plain in the second quadrant of the face of the moon, having a dark floor: about 60 miles (96 km) in diameter. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: plato (Thesaurus) platitudinous Platonic Related Content Daily Word Quiz: miscreant Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language