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:
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
Glassock describes the facilitator’s job as pushing a boulder: “It’s hardest when it’s yet to move,” he said.
From The Wall Street Journal ● Aug. 4, 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
Olympic rock climbing champion Toby Roberts - who won gold in the boulder and lead event at Paris 2024 - was also made an MBE on Tuesday.
From BBC ● May 5, 2026
After sending several boulders crashing to the depths far out of any human’s reach, Stais ordered that, even though it presented a risk to the Mykali, the next boulder should be hoisted to the surface.
From "Shipwrecked!" by Martin W. Sandler
Andrus’ parents, David and Martha, who is 72 years old, now live about 2 miles away after moving from Boulder, Colo., in May to be closer to both their sons.
From The Wall Street Journal ● Oct. 24, 2026
In August, human remains, including a jawbone with teeth and dental fillings and rib bones, were discovered at Boulder Beach in the Lake Mead National Recreation Area.
From Los Angeles Times ● Oct. 16, 2026
Kate Su of the Space Science Institute in Boulder, Colorado, led a team of astronomers that used Webb to investigate these unusual systems in greater detail.
From Science Daily ● Oct. 7, 2026
Yet Kevin Russell, representing Boulder County, argued that the lawsuit is a run-of-the-mill tort.
From The Wall Street Journal ● Oct. 6, 2026
Everything in East Hampden was dark and deserted, even the Boulder Tap; the only light for miles around seemed to be the light shimmering around the pay phone in front.
From "The Secret History" by Donna Tartt
The asteroid's boulders might contain far more empty space than scientists had assumed, allowing them to lose heat faster than ordinary solid rocks.
From Science Daily ● Oct. 20, 2026
Living shorelines, such as those along the Orange and San Diego county coasts, involve piling sand atop boulders or smaller stones and covering the berms with vegetation.
From Los Angeles Times ● Oct. 17, 2026
Before the building work started, the general was said to have rolled large boulders found at the summit - and ideally suit for construction - downhill.
From BBC ● Oct. 1, 2026
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
Ahead rose a number of high boulders and he warily guided the Crochan past them.
From "The Black Cauldron" by Lloyd Alexander
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Get a wordDefinitions 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.
