[em.bryo] n, pl em.bry.os [ML embryon-, embryo, fr. Gk embryon, fr. en- + bryein to swell; akin to Gk bryon catkin] (1548) 1 a archaic: a vertebrate at any stage of development prior to birth or hatching b: 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; esp: the developing human individual from the time of implantation to the end of the eighth week after conception
2: the young sporophyte of a seed plant usu. comprising a rudimentary plant with plumule, radicle, and cotyledons 3 a: something as yet undeveloped b: a beginning or undeveloped state of something "productions seen in ~ during their out-of-town tryout period --Henry Hewes"