1. an organism composed of two or more kinds of genetically dissimilar cells. For example, a chimera may have received a transplant of genetically different tissue, such as bone marrow, or it may have been produced by grafting an embryonic part of one animal onto the embryo of a genetically different animal; the graft may be either from a different species (a xenograft) or from a genetically nonidentical member of the same species (an allograft).

2. an illusion of the imagination, sometimes something desired but impossible to realize. —chimeric adj.