tannin

n. substance derived from certain plants (used in tanning hides and in medicine)

Tannins are astringent, bitter-tasting plant polyphenols that bind and precipitate proteins. The term tannin refers to the use of tannins in tanning animal hides into leather; however, the term is widely applied to any large polyphenolic compound containing sufficient hydroxyls and other suitable groups (such as carboxyls) to form strong complexes with proteins and other macromolecules. Tannins have molecular weights ranging from 500 to over 3,000.
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Noun
1. any of various complex phenolic substances of plant origin; used in tanning and in medicine
(synonym) tannic acid
(hypernym) phenol
(hyponym) cutch, kutch

n. tannin, astringent product of plants used for tanning hides and dyeing

(n.)
Same as Tannic acid, under Tannic.