Definition of illegal. : not according to or authorized by law : unlawful, illicit; also : not sanctioned by official rules (as of a game)
antibiotic. n. 1. (Pharmacology) any of various chemical substances, such as penicillin, streptomycin, chloramphenicol, and tetracycline, produced by various microorganisms, esp fungi, or made synthetically and capable of destroying or inhibiting the growth of microorganisms, esp bacteria. adj.
Medical Definition of Antimicrobial agent. Antimicrobial agent: A general term for drugs, chemicals, or other substances that either kill or slow the growth of microbes. Among the antimicrobial agents are antibacterial drugs, antiviral agents, antifungal agents, and antiparasitic drugs. Search MedTerms: