The Collaborative International Dictionary of English v.0.48:
Erythrosin \E*ryth"ro*sin\, n. [Gr. 'eryqro`s red.] (Chem.)
(a) A red substance formed by the oxidation of tyrosin.
(b) A red dyestuff obtained from fluoresce["i]n by the action
of iodine.
[1913 Webster]