an orange-red crystalline compound that in aqueous solution exhibits a greenish-yellow fluorescence in reflected light and is reddish-orange in transmitted light: used as a marker in sea water and as an indicator. Formula: C20H12O5
fluorescein in American English
(ˌfluəˈrɛsiɪn)
noun
a yellowish-red, crystalline compound, C20H12O5, made synthetically from resorcinol and phthalic anhydride: a dilute alkaline solution appears green by reflected light and red by transmitted light: used as a textile dye, a liquid coloring, and, in medicine, an intravenous diagnostic aid
Word origin
< fluoresce + -in1: from its bright fluorescence in solution