embryo

em·bryo

noun \ˈem-brē-ˌō\

plural em·bry·os

Definition of EMBRYO

1

archaic : a vertebrate at any stage of development prior to birth or hatching

2

: an animal in the early stages of growth and differentiation that are characterized by cleavage, the laying down of fundamental tissues, and the formation of primitive organs and organ systems; especially : the developing human individual from the time of implantation to the end of the eighth week after conception—compare fetus