The Collaborative International Dictionary
Petrous \Pe"trous\, a. [L. petrosus, fr. petra a stone.]
Like stone; hard; stony; rocky; as, the petrous part of the temporal bone.
--Hooper.(Anat.) Same as Petrosal.
Douglas Harper's Etymology Dictionary
1540s, from Middle French petreux, from Latin petrosus "stony," from petra "rock," from Greek petra "rock, cliff, ledge, shelf of rock, rocky ridge," of uncertain origin. Possibly from PIE root *per- "to lead, pass over," if the original meaning is "bedrock" and the notion is "what one comes through to" [Watkins].
Wiktionary
a. 1 Resembling rock or stone in its hardness 2 Of the dense portion of the temporal bone that protects the inner ear.
WordNet
adj. (of bone especially the temporal bone) resembling stone in hardness [syn: stonelike]
Usage examples of "petrous".
With bone forceps or a fine saw, split open the petrous portion of the temporal bone and observe the cochlea and the semicircular canals.
The inner projection of the temporal bone is known as the petrous process.
They even permitted him to regale them in Latin, and later, with growing incidence as years passed, he dashed their petrous visages with waves from distinctly pagan tongues, voluptuous Italian, which flowed over their northern souls like sunlit water over rocks.
Still, a number of gray petrous visages continued to appear, drawn on by a habit which they called duty, and perhaps, though none would have admitted it, a sort of perilous curiosity roused by this young man who invoked flesh and deity alike in whistling tones which bounced off their northern souls like shiny stones scaled over still water.
He had staining of the petrous ridge of the temporal bones and mastoid air cells, bilaterally.