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.
fourth nerve palsy This is a paralysis or stroke to the fourth cranial nerve. This nerve controls a single eye muscle called the superior oblique muscle. This muscle is located behind the eyeball and it helps the eye look downward and assists with eye rotation when you tilt your head sideways.