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.
antiseptic. 1. preventing sepsis. 2. any substance that inhibits the growth of bacteria, in contrast to a germicide, which kills bacteria outright. Antiseptics are not considered to include antibiotics, which are usually taken internally.