The Collaborative International Dictionary of English v.0.48:

Alder \Al"der\ ([add]l"d[~e]r), Aller \Al"ler\ ([add]l"l[~e]r),
   a. [From ealra, alra, gen. pl. of AS. eal. The d is
   excrescent.]
   Of all; -- used in composition; as, alderbest, best of all,
   alderwisest, wisest of all. [Obs.] --Chaucer.
   [1913 Webster] alderfly

The Collaborative International Dictionary of English v.0.48:

Alder \Al"der\ ([add]l"d[~e]r), n. [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.] (Bot.)
   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.
   [1913 Webster]

   Black alder.
   (a) A European shrub (Rhamnus frangula); Alder buckthorn.
   (b) An American species of holly (Ilex verticillata),
       bearing red berries.
       [1913 Webster] Alder

WordNet (r) 3.0 (2006):

alder
    n 1: wood of any of various alder trees; resistant to underwater
         rot; used for bridges etc
    2: north temperate shrubs or trees having toothed leaves and
       conelike fruit; bark is used in tanning and dyeing and the
       wood is rot-resistant [syn: alder, alder tree]

U.S. Gazetteer Places (2000):

Alder, MT -- U.S. Census Designated Place in Montana
   Population (2000):    116
   Housing Units (2000): 69
   Land area (2000):     2.013323 sq. miles (5.214482 sq. km)
   Water area (2000):    0.000000 sq. miles (0.000000 sq. km)
   Total area (2000):    2.013323 sq. miles (5.214482 sq. km)
   FIPS code:            00850
   Located within:       Montana (MT), FIPS 30
   Location:             45.324531 N, 112.108035 W
   ZIP Codes (1990):
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Alder, MT
    Alder