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from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. A large rounded mass of rock lying on the surface of the ground or embedded in the soil.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. A large piece of stone that can theoretically be moved if enough force is applied.
  • n. A particle greater than 256 mm in diameter, following the Wentworth scale
  • v. To engage in bouldering

from the GNU version of the Collaborative International Dictionary of English

  • n. Same as bowlder.

from The Century Dictionary and Cyclopedia

  • n. A loose rock, or one which has been torn from its native bed and transported to some distance.
  • To wear smooth, as an emery-wheel, by abrading with small flint pebbles. Also spelled bowlder.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • n. a large smooth mass of rock detached from its place of origin
  • n. a town in north central Colorado; Rocky Mountains resort center and university town


Middle English bulder, of Scandinavian origin; see bhel-2 in Indo-European roots.
(American Heritage® Dictionary of the English Language, Fourth Edition)
From Middle English bulder, possibly from Swedish bullersten ("noisy stone"), or possibly from Dutch bolder (Wiktionary)



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  • A lump of rock must be bigger than 256 millimetres (just over ten inches) to be a boulder, according to geologists' Udden-Wentworth scale.

    February 26, 2007