(n)early stage of an embryo produced by cleavage of an ovum; a liquid-filled sphere whose wall is composed of a single layer of cells; during this stage (about eight days after fertilization) implantation in the wall of the uterus occurs, Syn.blastosphere
The Collaborative International Dictionary of English (GCIDE) v.0.53Collaborative International Dictionary (GCIDE)
‖n. [ NL., dim. of Gr. blasto`s a sprout. ] (Biol.) That stage in the development of the ovum in which the outer cells of the morula become more defined and form the blastoderm. [ 1913 Webster ]