Rosetta stone

noun

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.

Rosetta stone

noun

1. 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

Rosetta stone

1. A stone discovered in Egypt (see also Egypt) in the late eighteenth century, inscribed with ancient Egyptian hieroglyphics and a translation of them in Greek. The stone proved to be the key to understanding Egyptian writing.

A “Rosetta stone” is the key to understanding a complex problem.