Definition of petrograph in English:

petrograph

Pronunciation /ˈpɛtrə(ʊ)ɡrɑːf/ /ˈpɛtrə(ʊ)ɡraf/

noun

  • A carving, especially writing, upon a rock; a rock inscription.

Origin

Early 19th century; earliest use found in Robert Southey (1774–1843), poet and reviewer. From petro- + -graph.