xanthene

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A yellow crystalline organic compound, C₁₃H₁₀O, that is soluble in ether and is used as a fungicide and in organic synthesis. The structural unit of xanthene is a feature in several fluorescent dyes.

from The Century Dictionary.

• noun Orthomethylenediphenylene oxid; a colorless compound, , prepared by the action of aluminium chlorid on phenol. It crystallizes in plates, melts at 100.5° C., and boils at 315° C.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun chemistry any of a group of tricyclic heterocycles (dibenzopyrans) that are the basis for a range of dyes such as fluorescein and eosin