lactic acid

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A syrupy, water-soluble liquid, C₃H₆O₃, produced in muscles as a result of anaerobic glucose metabolism, and present in sour milk, molasses, various fruits, and wines. A synthetic form of compound is used in foods and beverages as a flavoring and preservative, in dyeing and textile printing, and in pharmaceuticals.

Wiktionary

1. n. 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.

GNU Webster's 1913

1. adj. (Physiol. Chem.) a sirupy, colorless fluid, soluble in water, with an intensely sour taste and strong acid reaction. There is one center of optical activity, and this results in the observation of three isomeric modifications all having the formula C3H6O3; one is dextrorotatory (L-lactic acid), the other levorotatory (D-lactic acid), and the third an optically inactive mixture of the first two (DL-lactic acid); chemically it is 2-hydroxypropanoic acid. Sarcolactic acid or paralactic acid occurs chiefly in dead muscle tissue, while ordinary lactic acid (DL-lactic acid) results from fermentation, such as the fermentation of milk by lactic acid bacteria. The two acids are alike in having the same constitution (expressed by the name ethylidene lactic acid), but the latter is optically inactive, while sarcolactic acid rotates the plane of polarization to the right. The third acid, ethylene lactic acid, accompanies sarcolactic acid in the juice of flesh, and is optically inactive.

WordNet 3.0

1. n. a clear odorless hygroscopic syrupy carboxylic acid found in sour milk and in many fruits