a colorless, strong-smelling isomeric fatty acid, CHCHCHCOOH, found in rancid butter, perspiration, etc. and used to produce fragrances and flavors
See butyric acid in American Heritage Dictionary 4
noun
Either of two colorless isomeric acids, C3H7COOH, occurring in animal milk fats and used in disinfectants, emulsifying agents, and pharmaceuticals. Also called butanoic acid.