[L. ulmus, elm.] A substance obtained from the elm tree, of very singular properties. It resembles gum, but is hard of a black color, and considerably bitter. In its original state it is soluble in water, and insoluble in alcohol or ether; but when nitric or oxymuriatic acid is poured into its solution, it changes into a resinous substance no longer soluble in water, but soluble in alcohol.
A substance originally obtained in the state of an exsudation from the elm; but it is found to be a constituent of the bark of almost all trees.