Definition of petro- in US English:

petro-

combining form

  • 1Of rock; relating to rocks.

    ‘petrography’
  • 2Relating to petroleum.

    ‘petrodollar’

Origin

Petro- (sense 1) from Greek petros ‘stone’, petra ‘rock’; petro- (sense 2) from petroleum.

Pronunciation

petro-

/ˈpɛtroʊ//ˈpetrō/