(Science: botany) a tree, usually growing in moist land, and belonging to the genus Alnus. The wood is used by turners, etc.; the bark by dyers and tanners. In the u. S. The species of alder are usually shrubs or small trees. Black alder. A European shrub (rhamnus frangula); alder buckthorn. An American species of holly (ilex verticillata), bearing red berries.
Origin: oe. Aldir, aller, fr. As. Alr, aler, alor, akin to D. Els, g. Erle, Icel. Erlir, erli, Swed. Al, dan. Elle, el, L. Alnus, and E. Elm.