cephalin Syllabification: (ceph·a·lin)Pronunciation: /ˈsefəlin/Definition of cephalin noun Biochemistry any of a group of phospholipids present in cell membranes, especially in the brain. Origin: late 19th century: from Greek kephalē 'brain' + -in1cephalin in other Oxford dictionaries Definition of cephalin in the British & World English dictionary