Webster’s Revised Unabridged Dictionary · 1913
Ectoderm
Ec′to·derm, n. [Ecto- + -derm.] (Biol.) (a) The outer layer of the blastoderm; epiblast. (b) The external skin or outer layer of an animal or plant, this being formed in an animal from the epiblast. See Illust. of Blastoderm.