lactic acid

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

• noun A syrupy, water-soluble liquid, C₃H₆O₃, produced by anaerobic glucose metabolism in muscles, by certain bacteria, and by synthetic methods. Lactic acid is present in fermented foods such as yogurt and sauerkraut and is used in foods and beverages as a flavoring and preservative, in dyeing and textile printing, and in pharmaceuticals.

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

• noun organic chemistry 2-hydroxy-propanoic acid (CH3.CHOH.CO2H), a syrupy liquid, soluble in water; found in milk, wine and many fruits; used as a food additive and in many industrial applications.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a clear odorless hygroscopic syrupy carboxylic acid found in sour milk and in many fruits