Phenothiazine in which S is replaced by O; as the 3-oxo derivative (phenoxazone), phenoxazine is the chromophore of actinomycins. ... (05 Mar 2000) ... 
Type: Term Pronunciation: fe-nok′să-zēn Definitions: 1. Phenothiazine in which S is replaced by O; as the 3-oxo derivative (phenoxazone), phenoxazine is the chromophore of actinomycins.