adj. Of, relating to, caused by, or affecting life or living organisms: biological processes such as growth and digestion. adj. Having to do with biology.adj. Related by blood or genetic lineage: the child's biological parents; his biological sister. n. A preparation, such as a drug, a vaccine, or an antitoxin, that is synthesized from living organisms or their products and used medically as a diagnostic, preventive, or therapeutic agent.