Chimera

chi·me·ra also chi·mae·ra (kī-mîr'ə, kĭ-) n.

1. An organism, organ, or part consisting of two or more tissues of different genetic composition, produced as a result of organ transplant, grafting, or genetic engineering.
   
2. A substance, such as an antibody, created from the proteins or genes or two different species.
   
3. An individual who has received a transplant of genetically and immunologically different tissue.
   
4. A fanciful mental illusion or fabrication.

• [Middle English chimere, Chimera, from Old French, from Latin chimaera, from Greek khimaira, chimera, she-goat.]