- a combining form meaning “bud, sprout,” “embryo,” “formative cells or cell layer,” used in the formation of compound words: blastosphere.
- (in biology) indicating an embryo or bud or the process of buddingblastoderm
before vowels blast-, word-forming element used in scientific compounds to mean “germ, bud,” from Greek blasto-, comb. form of blastos “sprout, germ,” of unknown origin.
- Bud; germ; budding; germination:blastocyst.