oleic acid An unsaturated fatty acid with one double bond, CH 3 (CH 2 ) 7 CH:CH(CH 2 ) 7 COOH; r.d. 0.9; m.p. 13°C. Oleic acid is one of the most abundant constituent fatty acids of animal and plant fats, occurring in butterfat, lard, tallow, groundnut oil, soya-bean oil, etc. Its systematic ...