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.
Definition. 1  An antiseptic is a substance which inhibits the growth and development of microorganisms. 2  Antiseptics are a diverse class of drugs which are applied to skin surfaces or mucous membranes for their anti-infective effects.