1. 1. An organism in its early stages of development, especially before it has reached a distinctively recognizable form.
   2. An organism at any time before full development, birth, or hatching.
2. 1. The fertilized egg of a vertebrate animal following cleavage.
   2. In humans, the prefetal product of conception from implantation through the eighth week of development.
3. Botany. The minute, rudimentary plant contained within a seed or an archegonium.
4. A rudimentary or beginning stage: "To its founding fathers, the European [Economic] Community was the embryo of the United States of Europe" (Economist).

[Medieval Latin embryō, from Greek embruon : en-, in; see en-² + bruein, to be full to bursting.]

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.