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.
Cranial nerves (CN) I, II and VIII are primarily sensory related. 1  CN I, the olfactory nerve, carries information regarding smell from the nose to the brain. 2  CN II, the optic nerve, carries visual information to the brain for processing. 3  The vestibulocochlear nerve, CN VIII, controls hearing and balance.