WordReference Random House Unabridged Dictionary of American English © 2017
blas•to•cyst  (blastə sist),USA pronunciation n. [Embryol.]
  1. Developmental Biologythe blastula of the mammalian embryo, consisting of an inner cell mass, a cavity, and an outer layer, the trophoblast.
  • blasto- + -cyst 1885–90

'blastocyst' also found in these entries:

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