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Synonyms

boulder

1 American  
[bohl-der] / ˈboʊl dər /
Or bowlder

noun

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

Boulder 2 American  
[bohl-der] / ˈboʊl dər /

noun

  1. a city in N Colorado.

boulder British  
/ ˈbəʊldə /

noun

  1. 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

  2. geology a rock fragment with a diameter greater than 256 mm and thus bigger than a cobble

"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

Other Word Forms

  • bouldered adjective
  • bouldery adjective

Etymology

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

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

As Ryland works to translate Rocky’s language and build a system for the two to communicate, the bond formed between human and pentapedal boulder is palpable.

From Salon • Mar. 21, 2026

In her first picture, she stood in a one-piece on a boulder, smiling, a waterfall pummeling behind her.

From Los Angeles Times • Feb. 20, 2026

A 14-year-old girl decorated a large boulder off Greenland’s coast with the letters: “U.S.A. OK.”

From The Wall Street Journal • Jan. 24, 2026

This idea helped explain why foams appear stable once formed, much like a boulder resting at the bottom of a valley.

From Science Daily • Jan. 15, 2026

I flinched as the boulder bounced near us with a floor-rattling crash.

From "Tristan Strong Punches a Hole in the Sky" by Kwame Mbalia

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.