mesoblast Syllabification: (mes·o·blast)Pronunciation: /ˈmezəˌblast, ˈmē-/Definition of mesoblast noun Embryology the mesoderm of an embryo in its earliest stages. Derivatives mesoblasticPronunciation: /ˌmezəˈblastik, ˌmē-/ adjective mesoblast in other Oxford dictionaries Definition of mesoblast in the British & World English dictionary