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1. Any of various water-soluble polyphenols found in plant tissues that bind proteins and promote the tanning of leather. Also called tannic acid.
2. Any of various other substances that promote the tanning of leather, such as chromium salts.
[French, from tan, crushed oak bark, from Old French, from Medieval Latin tannum; see tan1.]
(Elements & Compounds) any of a class of yellowish or brownish solid compounds found in many plants and used as tanning agents, mordants, medical astringents, etc. Tannins are derivatives of gallic acid with the approximate formula C76H52O46. Also called: tannic acid
[C19: from French tanin, from tan1]
any of a group of astringent vegetable principles or compounds, chiefly complex glucosides of catechol and pyrogallol, as the reddish compound that gives tanning properties to oak bark or the whitish compound that occurs in nutgalls.Also called tan′nic ac′id.
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|Noun||1.||tannin - any of various complex phenolic substances of plant origin; used in tanning and in medicine|
phenol - any of a class of weakly acidic organic compounds; molecule contains one or more hydroxyl groups
catechin - a tannic acid that is extracted from black catechu as a white crystalline substance