Heterologous \Het`er*ol"o*gous\, a. [Hetero- + Gr. ? proportion.] Characterized by heterology; consisting of different elements, or of like elements in different proportions; different; -- opposed to homologous; as, heterologous organs. {Heterologous stimulus}. (Physiol.) See under {Stimulus}. {Heterologous tumor} (Med.), a tumor differing in structure from the normal tissues of the body.