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.
- Any of various deciduous shrubs or trees of the genus Alnus, native chiefly to northern temperate regions and having alternate simple toothed leaves and tiny fruits in woody, conelike catkins.
- The wood of these plants, used in carvings and for making furniture and cabinets.