lymphoblast Syllabification: (lym·pho·blast)Pronunciation: /ˈlimfəˌblast/Definition of lymphoblast noun Medicine an abnormal cell resembling a large lymphocyte, produced in large numbers in a form of leukemia. Derivatives lymphoblasticPronunciation: /ˌlimfəˈblastik/ adjective lymphoblast in other Oxford dictionaries Definition of lymphoblast in the British & World English dictionary