a colorless, sharp-smelling, liquid fatty acid, CHCHCOH, found in chyme and sweat, and produced from ethanol and carbon monoxide: used in making artificial flavors, perfume esters, preservatives, etc.
See propionic acid in American Heritage Dictionary 4
(prōˌpē-ŏnˈĭk)
noun
A liquid fatty acid, CH3CH2COOH, found naturally in sweat, in milk products, and as a product of bacterial fermentation. Prepared synthetically from ethyl alcohol and carbon monoxide, it is used chiefly in the form of its propionates as a mold inhibitor in bread and as an ingredient in perfume. Also called propanoic acid.