noun
1. : any of the series of saturated aliphatic monocarboxylic acids C n H 2 n +1 COOH (as acetic acid or lauric acid) many of which occur naturally usually in the form of esters in fats, waxes, and essential oils
2. : any of the saturated or unsaturated monocarboxylic acids that occur naturally in the form of glycerides in fats and fatty oils, that in almost all cases contain an even number of carbon atoms most commonly 12 to 24 in the higher acids (as palmitic acid or oleic acid), that in a few cases contain a substituting group (as hydroxyl in ricinoleic acid), that are obtained by hydrolysis of fats or by synthesis, and that are used chiefly in making soap, detergents, metallic soaps, and other derivatives