encephalomyelitis Syllabification: (en·ceph·a·lo·my·e·li·tis)Pronunciation: /enˌsefələˌmīəˈlītis/Definition of encephalomyelitis noun Medicine inflammation of the brain and spinal cord, typically due to acute viral infection. encephalomyelitis in other Oxford dictionaries Definition of encephalomyelitis in the British & World English dictionary