Definition from Wiktionary, the free dictionary
the Rosetta Stone
- A large inscribed stone found near Rosetta, Egypt, in 1799; later used as a basis for understanding many previously undecipherable examples of hieroglyphic writing.
- (by extension) Any source of information crucial to interpreting.
- My friend’s carefully-compiled notebook was the Rosetta Stone that opened understanding of the physics lectures.
large inscribed stone