The Collaborative International Dictionary hypoderm 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. Wiktionary hypoderm n. hypodermis