1. a. An organism in its early stages of development, especially before it has reached a distinctively recognizable form. b. An organism at any time before full development, birth, or hatching.
2. a. The fertilized egg of a vertebrate animal following cleavage. b. In human beings, 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).