macromyelonAnat.|ˌmækrəʊˈmaɪɪlɒn| [f. macro- + myelon.] Owen's name for the medulla oblongata. Hence macroˈmyelonala. 1846Owen Lect.Anat. Vertebrate Anim. Contents 9 ‘Macromyelon’ or Medulla Oblongata.1868― Anat. Vertebrates III. 83 The floor of the expanded macromyelonal canal.