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.
Function of Cranial Nerves. 1  Olfactory Nerve: Sense of smell. 2  Optic Nerve: Vision. 3  Oculomotor Nerve: Eyeball and eyelid movement. 4  Trochlear Nerve: Eye movement. 5  Trigeminal Nerve: This is the largest cranial nerve and is divided into three branches consisting of the ophthalmic, maxillary and mandibular nerves.