antibiotic /-otˈik/ adjective

1. Inimical to life
2. Inhibiting the growth of another organism, used esp of a substance produced by micro-organisms which, in dilute solution, has the capacity to inhibit the growth of, or to destroy, micro-organisms causing infectious diseases
3. Relating to antibiosis

An antibiotic substance

antibiotic resistance noun (biology)

A property of certain micro-organisms or cells which enables them to survive high concentrations of a normally lethal agent, usu acquired by the selection of a rare resistant mutant in the presence of low concentrations of the agent