Definition of: antibiotic

(an′ti·bī·ot′ik) noun
1. That which is antagonistic toward or destructive of life.
2. Biochem. a Any of a large class of substances produced by various micro-organisms and fungi that have the power of arresting the growth of other micro-organisms or of destroying them: some, as penicillin and streptomycin, are of value in the treatment of certain infectious diseases. b A chemical having similar properties produced by higher plants, some animals, and synthetically.