Real Dictionary

alder
variable noun: An alder is a species of tree or shrub that grows especially in cool, damp places and loses its leaves in winter.

alder in American English
any of a small group of rapidly growing trees and shrubs (genus Alnus) of the birch family, having toothed leaves and catkins, and growing in cool, moist soil in temperate and cold climates: the bark is used in dyeing and tanning, the wood is used for bri
noun: any shrub or tree belonging to the genus Alnus, of the birch family, growing in moist places in northern temperate or colder regions and having toothed, simple leaves and flowers in catkins

alder in British English
noun: any N temperate betulaceous shrub or tree of the genus Alnus, having toothed leaves and conelike fruits. The bark is used in dyeing and tanning and the wood for bridges, etc because it resists underwater rot