Definition of COUNTERBORE. : to form a counterbore in: enlarge (part of a hole) by means of a counterbore.ADVERTISEMENT.efinition of COUNTERBORE. 1. : a flat-bottomed enlargement of the mouth of a cylindrical bore. 2. : a drill for making a counterbore â compare countersink.
The vestibulocochlear nerve (auditory vestibular nerve) , known as the eighth cranial nerve, transmits sound and equilibrium (balance) information from the inner ear to the brain.
There are 12 cranial nerves, each of which is accorded a Roman numeral and a name: 1  Cranial nerve I: the olfactory nerve. 2  Cranial nerve II: the optic nerve. 3  Cranial nerve III: the oculomotor nerve.  Cranial nerve IV: the trochlear 1  nerve. Cranial nerve V: the trigeminal nerve.  Cranial nerve VI: the abducent 1  nerve. Cranial nerve VII: the facial  nerve.