before vowels blast-, word-forming element used in scientific compounds to mean "germ, bud," from Greek blasto-, combining form of blastos "sprout, germ," which is of unknown origin.
Entries linking to blasto-
blastocyst n.
a fertilized egg after about 5 or 6 days, when it is a ball of rapidly dividing cells, 1876, from blasto- + cyst.