The Collaborative International Dictionary of English v.0.48:

Bowlder \Bowl"der\, Boulder \Boul"der\, n. [Cf. Sw. bullra to
   roar, rattle, Dan. buldre, dial. Sw. bullersteen larger kind
   of pebbles; perh. akin to E. bellow.]
   [1913 Webster]
   1. A large stone, worn smooth or rounded by the action of
      water; a large pebble.
      [1913 Webster]

   2. (Geol.) A mass of any rock, whether rounded or not, that
      has been transported by natural agencies from its native
      bed. See Drift.
      [1913 Webster]

   Bowlder clay, the unstratified clay deposit of the Glacial
      or Drift epoch, often containing large numbers of
      bowlders.

   Bowlder wall, a wall constructed of large stones or
      bowlders.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Boulder \Boul"der\ (b[=o]l"d[~e]r), n.
   Same as Bowlder.
   [1913 Webster]

WordNet (r) 3.0 (2006):

boulder
    n 1: a large smooth mass of rock detached from its place of
         origin [syn: boulder, bowlder]
    2: a town in north central Colorado; Rocky Mountains resort
       center and university town

U.S. Gazetteer Counties (2000):

Boulder -- U.S. County in Colorado
   Population (2000):    291288
   Housing Units (2000): 119900
   Land area (2000):     742.460123 sq. miles (1922.962810 sq. km)
   Water area (2000):    8.911620 sq. miles (23.080988 sq. km)
   Total area (2000):    751.371743 sq. miles (1946.043798 sq. km)
   Located within:       Colorado (CO), FIPS 08
   Location:             40.058094 N, 105.195154 W
   Headwords:
    Boulder
    Boulder, CO
    Boulder County
    Boulder County, CO


U.S. Gazetteer Places (2000):

Boulder, WY -- U.S. Census Designated Place in Wyoming
   Population (2000):    30
   Housing Units (2000): 28
   Land area (2000):     1.301509 sq. miles (3.370893 sq. km)
   Water area (2000):    0.000000 sq. miles (0.000000 sq. km)
   Total area (2000):    1.301509 sq. miles (3.370893 sq. km)
   FIPS code:            09235
   Located within:       Wyoming (WY), FIPS 56
   Location:             42.748164 N, 109.712828 W
   ZIP Codes (1990):     82923
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Boulder, WY
    Boulder


U.S. Gazetteer Places (2000):

Boulder, MT -- U.S. town in Montana
   Population (2000):    1300
   Housing Units (2000): 568
   Land area (2000):     1.137662 sq. miles (2.946530 sq. km)
   Water area (2000):    0.000000 sq. miles (0.000000 sq. km)
   Total area (2000):    1.137662 sq. miles (2.946530 sq. km)
   FIPS code:            08575
   Located within:       Montana (MT), FIPS 30
   Location:             46.236300 N, 112.121823 W
   ZIP Codes (1990):     59632
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Boulder, MT
    Boulder


U.S. Gazetteer Places (2000):

Boulder, CO -- U.S. city in Colorado
   Population (2000):    94673
   Housing Units (2000): 40726
   Land area (2000):     24.374601 sq. miles (63.129925 sq. km)
   Water area (2000):    0.996658 sq. miles (2.581332 sq. km)
   Total area (2000):    25.371259 sq. miles (65.711257 sq. km)
   FIPS code:            07850
   Located within:       Colorado (CO), FIPS 08
   Location:             40.019425 N, 105.259502 W
   ZIP Codes (1990):     80301 80302 80303 80304
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Boulder, CO
    Boulder


U.S. Gazetteer Places (2000):

Boulder, UT -- U.S. town in Utah
   Population (2000):    180
   Housing Units (2000): 102
   Land area (2000):     20.918639 sq. miles (54.179024 sq. km)
   Water area (2000):    0.000000 sq. miles (0.000000 sq. km)
   Total area (2000):    20.918639 sq. miles (54.179024 sq. km)
   FIPS code:            07470
   Located within:       Utah (UT), FIPS 49
   Location:             37.924329 N, 111.426240 W
   ZIP Codes (1990):     84716
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Boulder, UT
    Boulder