/awl"deuhr/ , n.
1. 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.
2. any of various trees or shrubs resembling an alder.
[ bef. 900; ME alder, aller, OE alor, al ( e ) r; c. ON olr, MLG al ( l ) er álusó; akin to MHG alze alúso, OHG elira, erila (G Erle ) álisó, MLG els ( e ) alíso, hence Gmc * álus, alíso; cf. Pol olcha, Russ ol'khá alisa; Lith alksnis, L alnus alsnos ]