ole·in \ˈōlēə̇n\noun (-s) Etymology: French oléine, from olé- ole- + -ine 1.: an ester of glycerol and oleic acid; especially: triolein 2.alsoole·ine\“, -ēˌēn\ a.: the liquid portion of any fat — distinguished from stearin b.: sulfonated oil c.: commercial oleic acid < white olein > — compare red oil 1a