- 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.
- a clue, breakthrough, or discovery that provides crucial knowledge for the solving of a puzzle or problem.
- a basalt slab discovered in 1799 at Rosetta, dating to the reign of Ptolemy V (196 bc) and carved with parallel inscriptions in Egyptian hieroglyphics, demotic characters, and Greek, which provided the key to the decipherment of ancient Egyptian texts
