eosin(n = noun.substance) bromeosin - a red fluorescent dye resulting from the action of bromine on fluorescein; used in cosmetics and as a biological stain for studying cell structures;
A yellow or brownish red dyestuff obtained by the action of bromine on fluoresceïn, and named from the fine rose-red which it imparts to silk. It is also used for making a fine red ink. Its solution is fluorescent. [1913 Webster]