(em′brē·ō) noun plural ·os
1. The germ or rudimentary form of anything in its earliest stage; specifically, the germ of an organism before it has developed its distinctive form.
2. The germ of a viviparous animal in the first stages of its existence (in the human species the first two months).
3. Bot. The rudimentary plant within the seed, which makes its appearance soon after fertilization of the ovule by the pollen and then passes through a period of rest until the germination or sprouting of the seed. Also em′bry·on (-on).
—in embryo In an undeveloped or incipient stage or state; not yet developed or advanced, as a project or undertaking. For illustrations see under EGG, EMBRYOLOGY, FROG.
—adjective Pertaining to an embryo; rudimentary: also em′bry·al. [<Gk. embryon <en- in + bryein swell]

Embryo; embryonic: embryogenesis. Also, before vowels, embry-. [<Gk. embryon embryo]