boulder
noun
a detached and rounded or worn rock, especially a large one.
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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:
The Los Angeles neighborhood, which gets its name from a massive boulder in the hills that resembles the face of an eagle, is sandwiched between Pasadena and Glendale and two major freeways.
From Los Angeles Times ● Sep. 9, 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
Company dancer Lloyd Knight, costumed as the Preacher in “Spring” and captured in a determined stance on a boulder, faces the book’s last page, which quotes Graham: “Dancers are the messengers of the gods.”
From The Wall Street Journal ● Jun. 9, 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
Taking a small boulder, he jammed the entrance slab from swinging shut.
From "Redwall" by Brian Jacques
The latest discovery came Sunday at Boulder Beach on the western part of the Lake Mead National Recreation Area in Nevada, according to national park officials.
From Los Angeles Times ● Aug. 19, 2026
The US National Park Service said it received reports of apparent skeletal remains at Boulder Beach on Lake Mead, Nevada, on 16 August.
From BBC ● Aug. 19, 2026
Ann Lipton, a law professor at the University of Colorado, Boulder, said Trump knows the value of his statements and that the more he rattles markets, the more valuable his new service becomes.
From Barron's ● Aug. 4, 2026
The discoveries were made by researchers at the University of Warwick and the University of Colorado Boulder.
From Science Daily ● Jul. 15, 2026
I lie still, waiting for this mystery monster, whatever made Boulder and Maple disappear.
From "Wayward Creatures" by Dayna Lorentz
As the waves bashed the coast this week, boulders smashed into the piles of Mitchell Leib’s Malibu home, plucking them like a “guitar string” and shaking his house.
From Los Angeles Times ● Sep. 11, 2026
Upper Trishuli 1 was constructed for water flows, not a massive debris-laden surge like in the August disaster, with boulders as big as 25 feet across, he said.
From The Wall Street Journal ● Sep. 9, 2026
"There's boulders bigger than houses - I've never seen that before in my life. It's just an extraordinary operation," the former head of the International Tunnelling Association said.
From BBC ● Aug. 31, 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
I take off running down the beach, jumping over shells and boulders and strands of kelp.
From "I Can Make This Promise" by Christine Day
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.
