trigeminal nerve Syllabification: (tri·gem·i·nal nerve)Pronunciation: /trīˈjemənl/Definition of trigeminal nerve noun Anatomy each of the fifth and largest pair of cranial nerves, supplying the front part of the head and dividing into the ophthalmic, maxillary, and mandibular nerves. trigeminal nerve in other Oxford dictionaries Definition of trigeminal nerve in the British & World English dictionary