or bowl·der



a detached and rounded or worn rock, especially a large one.

Origin of boulder

1610–20; short for boulder stone; Middle English bulderston < Scandinavian; compare dialectal Swedish bullersten big stone (in a stream), equivalent to buller rumbling noise (< Old Swedish bulder) + sten stone
Related formsboul·dered, adjectiveboul·der·y, adjective
Can be confusedbolder boulderboulder cobblestone granule pebble rock stone




a city in N Colorado. Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for boulder

Contemporary Examples of boulder

Historical Examples of boulder

  • We dropped behind a boulder and Tse-tse counted while I lifted every scent.

    The Trail Book

    Mary Austin

  • Linda rushed to the boulder and knelt again, but she could get no response to her questions.

    Her Father's Daughter

    Gene Stratton-Porter

  • He stooped; seized a boulder, hurled it at the oncoming Lee.

    The World Beyond

    Raymond King Cummings

  • He was behind a boulder, not too dissimilar to Calhoun's breastwork.

    Pariah Planet

    Murray Leinster

  • The girl stumbled, struck her head against a boulder, and lay still.

    Loot of the Void

    Edwin K. Sloat

British Dictionary definitions for boulder



a smooth rounded mass of rock that has a diameter greater than 25cm and that has been shaped by erosion and transported by ice or water from its original position
geology a rock fragment with a diameter greater than 256 mm and thus bigger than a cobble
Derived Formsbouldery, adjective

Word Origin for boulder

C13: probably of Scandinavian origin; compare Swedish dialect bullersten, from Old Swedish bulder rumbling + sten stone
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for boulder

1670s, variant of Middle English bulder (c.1300), from a Scandinavian source akin to Swedish dialectal bullersten "noisy stone" (large stone in a stream, causing water to roar around it), from bullra "to roar" + sten "stone." Or the first element might be from *buller- "round object," from Proto-Germanic *bul-, from PIE *bhel- (2) "to inflate, swell" (see bole).

Online Etymology Dictionary, © 2010 Douglas Harper