O"le*in (?), n. [L. oleum oil: cf. F. oléine.] (Physiol. Chem.) A fat, liquid at ordinary temperatures, but solidifying at temperatures below 0° C., found abundantly in both the animal and vegetable kingdoms (see Palmitin). It dissolves solid fats, especially at 30-40° C. Chemically, olein is a glyceride of oleic acid; and, as three molecules of the acid are united to one molecule of glyceryl to form the fat, it is technically known as triolein. It is also called elain.