embryo

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The collection of cells that has developed from the fertilized egg of a vertebrate animal, before all the major organs have developed.
• noun A collection of such cells of a human, especially from implantation in the uterine wall through the eighth week of development.
• noun Botany The young sporophytic plant contained within a seed or an archegonium.
• noun An organism at any time before full development, birth, or hatching.
• noun A rudimentary or beginning stage.

from The Century Dictionary.

• noun The fecundated germ of an animal in its earlier stages of development, and before it has assumed the distinctive form and structure of the parent; a germ; a rudiment; in a more extended sense, a rudimentary animal during its whole antenatal existance.
• noun In botany, the rudimentary plant contained in the seed, the result of the action of pollen upon the ovule.
• noun The beginning or first state of anything, while yet in a rude and undeveloped condition; the condition of anything which has been conceived but is not yet developed or executed; rudimentary state: chiefly in the phrase in embryo.
• noun Synonyms Fetus, Germ, Rudiment. The first of these words is mainly applied to the embryos of viviparous vertebrates in the later stages of their development, when they are more subject to observation. Germ means especially the seed or fecundated ovum, and scarcely extends beyond the early stages of an embryo. Rudiment is simply the specific application of a more general term to a germ or to the early, crude, or ‘rude’ stages of an embryo.
• Being in the first or rudimentary stage of growth or development; incipient; embryonic: as, an embryo flower.

from the GNU version of the Collaborative International Dictionary of English.

• noun The young of an animal in the womb, or more specifically, before its parts are developed and it becomes a fetus (see fetus).
• noun The germ of the plant, which is inclosed in the seed and which is developed by germination.
• noun in an incipient or undeveloped state; in conception, but not yet executed.
• adjective Pertaining to an embryo; rudimentary; undeveloped.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun In the reproductive cycle, the stage after the fertilization of the egg that precedes the development into a fetus.
• noun An organism in the earlier stages of development before it emerges from the egg, or before metamorphosis.
• noun In viviparous animals, the young animal's earliest stages in the mother's body
• noun In humans, usually the cell growth up to the end of the seventh week in the mother's body
• noun botany A rudimentary plant contained in the seed.
• noun The beginning; the first stage of anything.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun an animal organism in the early stages of growth and differentiation that in higher forms merge into fetal stages but in lower forms terminate in commencement of larval life
• noun (botany) a minute rudimentary plant contained within a seed or an archegonium