phloroglucin

from The Century Dictionary.

• noun A substance widely distributed in the vegetable kingdom, when pure crystallizing in small yellow crystals with the composition C₆H₃(OH)₃; a trivalent phenol. It is used in microscopy as one of the best reagents for testing lignified cell-walls.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Chem.) A sweet white crystalline substance, metameric with pyrogallol, and obtained by the decomposition of phloretin, and from certain gums, as catechu, kino, etc. It belongs to the class of phenols. [Called also phloroglucinol.]

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

• noun organic chemistry A white crystalline phenol, metameric with pyrogallol, obtained by the decomposition of phloretin and from certain gums.