boulder
noun
a detached and rounded or worn rock, especially a large one.
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bouilder.
boulder
1 American
[bohl-der]
/ ˈboʊl dər /
Or
bowlder
noun
-
boulders
plural
Boulder
2
American
[bohl-der]
/ ˈboʊl dər /
noun
boulder
British
/ ˈbəʊldə /
noun
-
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
Other Word Forms
Derived Forms
Inflected Forms
Nouns
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
Explanation
A boulder is a rock — a big one. Scientists often think of a boulder in more technical terms than we do. They use the word to describe not just a big rock, but a rock that some natural force — a river, a glacier or the like — has moved from its original location to its present one. A good way to remember all this is to think of Boulder, a city in Colorado that stands in the middle of the Rocky Mountains, and is, no doubt, full of boulders.
Vocabulary lists containing boulder
"Mending Wall," by Robert Frost
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Earth Science - Middle School
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Earth Science - High School
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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.
See Examples For:
He also provided entertainment, including a child playing Beethoven on piano outside the boulder, for people who flocked to the conventions.
From Los Angeles Times ● Sep. 1, 2026
I watch my 10 year old daughter Zena races through heather nearby, building boulder bridges over a cold stream, clinging to my brother as the Etive Mòr and Black Mount mountains rise behind them.
From BBC ● Aug. 26, 2026
Larger incoming objects, such as boulder sized rocks that create especially bright flashes, are known as bolides or fireballs.
From Science Daily ● May 14, 2026
The Zunis rained stones down on the invaders; one well-aimed boulder struck Coronado’s helmet.
From The Wall Street Journal ● Apr. 28, 2026
He stopped at a giant boulder beside the trail, where Python lay in the sun.
From "Tristan Strong Punches a Hole in the Sky" by Kwame Mbalia
Not long after Oxford’s confession, authorities tracked down Travis, who was in jail for an unrelated warrant in Boulder, Colorado, and had him extradited to Oklahoma.
From Slate ● Sep. 17, 2026
Visitors at Boulder Beach would stumble on human remains on three different occasions from July to August 2022 that authorities said all belonged to the same person, Claude Russell Pensinger, a Las Vegas resident.
From Los Angeles Times ● Aug. 19, 2026
Researchers led by chemists at the University of Wisconsin-Madison, working with teams at Colorado State University and the University of Colorado Boulder, have now demonstrated a different approach to reaction design.
From Science Daily ● Aug. 9, 2026
Mr. Pasnau is a philosophy professor at the University of Colorado, Boulder.
From The Wall Street Journal ● Jul. 23, 2026
One bitter night I tried to call my parents from the pay phone outside the Boulder Tap; sleet was falling and I was shivering so violently I could hardly get the coins in the slot.
From "The Secret History" by Donna Tartt
Soon they’d fill with water, and with what writer McPhee called “rock porridge,” a cold rolling lava of mud and debris and boulders the size of Volkswagens.
From Los Angeles Times ● Sep. 17, 2026
Photographs shared by the disaster office showed workers wading through churned mud and navigating vast boulders left by the floods.
From Barron's ● Aug. 30, 2026
Its stone fireplace comes to rest on what appear to be colossal boulders deposited by the last vagabond glacier.
From The Wall Street Journal ● Aug. 28, 2026
It will use one of its ships to drop boulders onto the seabed creating physical barriers to restrict access.
From BBC ● Jun. 22, 2026
Soon enough we pass between these huge boulders and come to a tall fence that crosses the trail and runs all the way to the ocean.
From "Clairboyance" by Kristiana Kahakauwila
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.
