define petrology
Definition of PETROLOGY. : a science that deals with the origin, history, occurrence, structure, chemical composition, and classification of rocks. â petÂ·roÂ·logÂ·ic \Ëpe-trÉ-Ëlae-ËlÃ¤\ jik orÂ·petÂ·roÂ·logÂ·i \-cal-ji\ kÉl. adjective