The Collaborative International Dictionary of English v.0.48:

Box \Box\ (b[o^]ks), n. [As. box, L. buxus, fr. Gr. ?. See Box
   a case.] (Bot.)
   A tree or shrub, flourishing in different parts of the world.
   The common box (Buxus sempervirens) has two varieties, one
   of which, the dwarf box (Buxus suffruticosa), is much used
   for borders in gardens. The wood of the tree varieties, being
   very hard and smooth, is extensively used in the arts, as by
   turners, engravers, mathematical instrument makers, etc.
   [1913 Webster]

   Box elder, the ash-leaved maple (Negundo aceroides), of
      North America.

   Box holly, the butcher's broom (Russus aculeatus).

   Box thorn, a shrub (Lycium barbarum).

   Box tree, the tree variety of the common box.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Elder \El"der\, n. [OE. ellern, eller, AS. ellen, cf. LG.
   elloorn; perh. akin to OHG. holantar, holuntar, G. holunder;
   or perh. to E. alder, n.] (Bot.)
   A genus of shrubs (Sambucus) having broad umbels of white
   flowers, and small black or red berries.
   [1913 Webster]

   Note: The common North American species is Sambucus
         Canadensis; the common European species (S. nigra)
         forms a small tree. The red-berried elder is S.
         pubens. The berries are diaphoretic and aperient. The
         European elder (Sambucus nigra) is also called the
         elderberry, bourtree, Old World elder, black
         elder, and common elder.
         [1913 Webster + WordNet 1.5]

   Box elder. See under 1st Box.

   Dwarf elder. See Danewort.

   Elder tree. (Bot.) Same as Elder. --Shak.

   Marsh elder, the cranberry tree Viburnum Opulus).
      [1913 Webster]

WordNet (r) 3.0 (2006):

box elder
    n 1: common shade tree of eastern and central United States
         [syn: box elder, ash-leaved maple, Acer negundo]

U.S. Gazetteer Counties (2000):

Box Elder -- U.S. County in Utah
   Population (2000):    42745
   Housing Units (2000): 14209
   Land area (2000):     5723.343217 sq. miles (14823.390253 sq. km)
   Water area (2000):    1005.688982 sq. miles (2604.722395 sq. km)
   Total area (2000):    6729.032199 sq. miles (17428.112648 sq. km)
   Located within:       Utah (UT), FIPS 49
   Location:             41.595787 N, 112.480319 W
   Headwords:
    Box Elder
    Box Elder, UT
    Box Elder County
    Box Elder County, UT


U.S. Gazetteer Places (2000):

Box Elder, MT -- U.S. Census Designated Place in Montana
   Population (2000):    794
   Housing Units (2000): 190
   Land area (2000):     5.748032 sq. miles (14.887334 sq. km)
   Water area (2000):    0.000000 sq. miles (0.000000 sq. km)
   Total area (2000):    5.748032 sq. miles (14.887334 sq. km)
   FIPS code:            08725
   Located within:       Montana (MT), FIPS 30
   Location:             48.307210 N, 110.002873 W
   ZIP Codes (1990):     59521
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Box Elder, MT
    Box Elder


U.S. Gazetteer Places (2000):

Box Elder, SD -- U.S. city in South Dakota
   Population (2000):    2841
   Housing Units (2000): 1072
   Land area (2000):     5.802230 sq. miles (15.027706 sq. km)
   Water area (2000):    0.003620 sq. miles (0.009375 sq. km)
   Total area (2000):    5.805850 sq. miles (15.037081 sq. km)
   FIPS code:            06620
   Located within:       South Dakota (SD), FIPS 46
   Location:             44.115349 N, 103.081997 W
   ZIP Codes (1990):     57719
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Box Elder, SD
    Box Elder