Any of various chemically different substances capable of promoting tanning.(noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "tannin" in a sentence
"The preparation of pentagalloyl glucose has proved this compound to be nearly identical with tannin obtained from galls (_tannin_); a few other natural tannins belong to this type which Fischer terms acyl compounds of sugar with hydroxybenzoic acids."
"The term tannin comes from the use of plant extracts in the tanning of leather which bind protein to form insoluble tannin-protein complexes."
"In the final blend you sometimes need grapes with too much acidity and tannin, in other words, grapes that might be left on the sorting room floor today."