target organ. Definitions: 1. a tissue or organ on which a hormone exerts its action; generally, a tissue or organ with appropriate receptors for a hormone. Synonyms: target3. The definition information for target organ is provided by Stedman's.You can search our medical dictionary here.. a tissue or organ on which a hormone exerts its action; generally, a tissue or organ with appropriate receptors for a hormone. Synonyms: target3. The definition information for target organ is provided by Stedman's.