actinomycin d, n. [From actinomyces, the genus of the organism in which they were first found.].
The most well-known of the actinomycins (C62H86N12O16), a class of antibiotics which act by binding to DNA and inhibiting synthesis of RNA; they act agains gram-positive bacteria and many eukaryotic organisma. Actinomycin D has been used in human medicine to treat certain tumors. [PJC]