petrous

1. Of, relating to, or resembling rock, especially in hardness; stony.
2. Of or relating to the very dense, hard portion of the temporal bone that forms a protective case for the inner ear.

[Middle English, from Old French petros, from Latin petrōsus, rocky, from petra, rock, from Greek petrā.]

1. Of stony hardness.
2. Of or relating to the dense hard portion of the temporal bone that forms a protective case for the inner ear.

Resembling rock or stone; stony.

• p. bone — the pars petrosa, or petrous portion of the temporal bone.

The adjective has one meaning:

Meaning #1: (of bone especially the temporal bone) resembling stone in hardness
  Synonym: stonelike