lactic acid
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 the compound is used in foods and beverages as a flavoring and preservative, in dyeing and textile printing, and in pharmaceuticals.
Source: The American Heritage® Dictionary of the English Language, Fourth Edition
Copyright © 2000 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.

lactic acid

Lactic \Lac"tic\, a. [L. lac, lactis, milk: cf. F. lactique. See Lacteal, and cf. Galactic.] (Physiol. Chem.) Of or pertaining to milk; procured from sour milk or whey; as, lactic acid; lactic fermentation, etc.

Lactic acid (Physiol. Chem.), a sirupy, colorless fluid, soluble in water, with an intensely sour taste and strong acid reaction. There are at least three isomeric modifications all having the formula C3H6O3. Sarcolactic or paralactic acid occurs chiefly in dead muscle tissue, while ordinary lactic acid results from fermentation. 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.

Source: Webster's Revised Unabridged Dictionary, © 1996, 1998 MICRA, Inc.

lactic acid

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

Source: WordNet ® 1.6, © 1997 Princeton University