Definition of white alder in US English:

white alder

noun

  • 1An alder, especially Alnus rhombifolia, of western North America.

  • 2The South African tree Platylophus trifoliatus (family Cunoniaceae).

  • 3A white-flowering shrub of moist habitats, Clethra alnifolia (family Clethraceae) native to eastern North America; also called sweet pepperbush.

Origin

Mid 18th century; earliest use found in Thomas Short (c1690–1772), physician.