- The post-fertilization occurrence of two or more cell lines with different genetic or chromosomal constitutions within a single individual or tissue.
Definition from: GeneReviews
from the University of Washington and the National Center for Biotechnology Information
- An organism or one of its parts composed of cells of more than one genotype.
Definition from: Merriam-Webster's Medical Dictionary by Merriam-Webster Inc.
Related discussion in the Handbook
See also Understanding Medical Terminology.