- 1: Growing from or on the outside (as in exogenous spores).
2: Caused by factors (as food or a traumatic factor) or an agent (as a disease-producing organism) from outside the organism or system (as in exogenous obesity, exogenous psychic depression).
3: Introduced from or produced outside the organism or system; specifically: not synthesized within the organism or system.
Definition from: Merriam-Webster's Medical Dictionary by Merriam-Webster Inc.
Related discussion in the Handbook
See also Understanding Medical Terminology.