Source : Webster's Revised Unabridged Dictionary (1913)

Hypoblast \Hy"po*blast\, n. [Pref. hypo- + -blast.] (Biol.)
   The inner or lower layer of the blastoderm; -- called also
   {endoderm}, {entoderm}, and sometimes {hypoderm}. See Illust.
   of {Blastoderm}, {Delamination}, and {Ectoderm}.

Source : WordNet®

hypoblast
     n : the inner germ layer that develops into the lining of the
         digestive and respiratory systems [syn: {endoderm}, {entoderm},
          {endoblast}, {entoblast}]