Source : Webster's Revised Unabridged Dictionary (1913)

Mesoblast \Mes"o*blast\, n. [Meso- + -blast.] (Biol.)
   (a) The mesoderm.
   (b) The cell nucleus; mesoplast.

Source : WordNet®

mesoblast
     n : the middle germ layer that develops into muscle and bone and
         cartilage and blood and connective tissue [syn: {mesoderm}]