Definition of rock oil in English:

rock oil

noun

historical
  • Petroleum, crude oil.

Origin

Mid 17th century; earliest use found in Walter Charleton (1620–1707), physician and natural philosopher. From rock + oil, ultimately after post-classical Latin petroleum petroleum. Compare German Steinöl, early modern Danish, Danish stenolie, Swedish stenolja, all now historical, which likewise show calques on the Latin word.

Pronunciation

rock oil

/ˈrɒk ɔɪl/