| a semisynthetic broad-spectrum antibiotic, C4 3H5 8N4O1 2, used in the treatment of pulmonary tuberculosis, asymptomatic carriers of meningococcal disease, and leprosy. |

rifampin ri·fam·pin (rĭ-fām'pĭn) or ri·fam·pi·cin (-pĭ-sĭn)
n.
A semisynthetic antibiotic, derived from a form of rifamycin, that interferes with the synthesis of RNA and is used to treat bacterial and viral diseases.