ketone body

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

• noun A ketone-containing substance, such as acetoacetic acid, that is an intermediate product of fatty acid metabolism. Ketone bodies tend to accumulate in the blood and urine of individuals affected by starvation or uncontrolled diabetes mellitus.

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

• noun biochemistry Any of several compounds that are intermediates in the metabolism of fatty acids; principally acetoacetate and acetone (together with hydroxybutyrate which is not a ketone)

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

• noun a ketone that is an intermediate product of the breakdown of fats in the body; any of three compounds (acetoacetic acid, acetone, and/or beta-hydroxybutyric acid) found in excess in blood and urine of persons with metabolic disorders