Definition of petrosal:
(adj) :
(anatomy, relational) Of, pertaining to, or located near the petrous part of the temporal bone or the capsule of the inner ear.
(n) :
(anatomy) The petrous part of the temporal bone at the base of the skull, surrounding the inner ear.
(n) :
(anatomy, zootomy) The auditory capsule.
(adj) :
Of great hardness; petrous.