any of several toxic antibiotics obtained from bacteria of the genus Streptomyces, used in treating some cancers; the most commonly used is dactinomycin (actinomycin D)
actinomycin in American English
(ˌæktənoʊˈmaɪsɪn)
US
noun
any of various antibiotic polypeptides derived from streptomyces soil bacteria: active against certain bacteria and fungi and some neoplasms