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.
Sixth cranial nerve palsy is weakness of the nerve that innervates the lateral rectus muscle. The lateral rectus muscle rotates the eye away from the nose and when the lateral rectus muscle is weak, the eye crosses inward toward the nose (esotropia).