The Collaborative International Dictionary of English v.0.48:

Ectoblast \Ec"to*blast\, n. [Ecto- + Gr. ? bud, germ.] (Biol.)
   (a) The outer layer of the blastoderm; the epiblast; the
       ectoderm.
   (b) The outer envelope of a cell; the cell wall. --Agassiz.
       [1913 Webster]

WordNet (r) 3.0 (2006):

ectoblast
    n 1: the outer germ layer that develops into skin and nervous
         tissue [syn: ectoderm, exoderm, ectoblast]