petrous

/ˈpɛtrəs/
adjective
  1. Relating to or resembling rock; hard and stony.
    • The old castle was built on a petrous foundation that had lasted for centuries.
    • The petrous surface of the cliff was impossible to climb without equipment.
    • Geologists studied the petrous layers of the ancient mountain range.
  2. Relating to the dense, hard part of the temporal bone in the skull.
    • The surgeon carefully avoided the petrous region during the operation.
    • The petrous part of the temporal bone protects the inner ear.
    • A fracture of the petrous bone can cause hearing loss.
Antonyms
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