Source : Webster's Revised Unabridged Dictionary (1913)

Blastomere \Blas"to*mere\, n. [Gr. blasto`s sprout + -mere.]
   (Biol.)
   One of the segments first formed by the division of the ovum.
   --Balfour.

Source : WordNet®

blastomere
     n : any cell resulting from cleavage of a fertilized egg