[fatty acid] n (ca. 1872) 1: any of numerous saturated aliphatic monocarboxylic acids (as acetic acid) including many that occur naturally usu. in the form of esters in fats, waxes, and essential oils
2: any of the saturated or unsaturated monocarboxylic acids (as palmitic acid) usu. with an even number of carbon atoms that occur naturally in the form of glycerides in fats and fatty oils