Source : Webster's Revised Unabridged Dictionary (1913)

Blastopore \Blas"to*pore\, n. [Gr. blasto`s sprout + E. pore.]
   (Biol.)
   The pore or opening leading into the cavity of invagination,
   or archenteron.

   Note: [See Illust. of {Invagination}.] --Balfour.

Source : WordNet®

blastopore
     n : the opening into the archenteron