Rosetta stone: Meaning and Definition of

Roset'ta stone"

Pronunciation: [key]
  1. a stone slab, found in 1799 near Rosetta, bearing parallel inscriptions in Greek, Egyptian hieroglyphic, and demotic characters, making possible the decipherment of ancient Egyptian hieroglyphics.
  2. a clue, breakthrough, or discovery that provides crucial knowledge for the solving of a puzzle or problem.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.