| gastrula | (n) double-walled stage of the embryo resulting from invagination of the blastula; the outer layer of cells is the ectoderm and the inner layer differentiates into the mesoderm and endoderm |
| gastrulation | (n) the process in which a gastrula develops from a blastula by the inward migration of cells |
| Gastrula | ‖n.; |
| Gastrulation | n. (Biol.) The process of invagination, in embryonic development, by which a gastrula is formed. [ 1913 Webster ] |