oxaloacetic acid

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

• noun A colorless crystalline dicarboxylic acid, C₄H₄O₅, that is formed by oxidation of malic acid in the Krebs cycle and by transamination from aspartic acid. It is important as an intermediate in the metabolism of carbohydrates and a precursor in the synthesis of amino acids.

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

• noun biochemistry on of the constituents of the citric acid cycle, formed by the oxidation of malic acid and via the transamination of aspartic acid; an intermediate in the synthesis of amino acids and the metabolism of carbohydrates
• noun organic chemistry a colourless crystalline organic carboxylic acid, butan-2-one-1,4-dicarboxylic acid, COOH.CH2.CO.COOH

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

• noun an acid formed by oxidation of maleic acid (as in metabolism of fats and carbohydrates)