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:
One man rides a draft horse dragging a wooden harrow, weighted down by a boulder, to break up the soil.
From The Wall Street Journal ● Sep. 29, 2026
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
"It was just timing. The boulder that actually took Jack, it could have gone in a week's time, a year's time - it just happened to go then and there."
From BBC ● May 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
At the bottom of a boulder she found the first victim.
From "A Girl Named Disaster" by Nancy Farmer
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
Last year, the Colorado Supreme Court ruled that Boulder County may sue for damages in a local court.
From Los Angeles Times ● Oct. 5, 2026
Boulder County’s lawsuit is not some novel attempt by a municipality to regulate greenhouse emissions around the world, and it does not purport to control any activity outside of its borders.
From Slate ● Oct. 5, 2026
I decided I should, and my hand was on the greasy brass door handle when I saw the name of the place in the window: Boulder Tap.
From "The Secret History" by Donna Tartt
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
Abandoning the vehicle, the group clambered up the rocky mountainside, grabbing onto boulders and grass to haul themselves up.
From The Wall Street Journal ● Sep. 9, 2026
By this time, several archaeologists had joined the expedition and immediately ordered that the powerful naval vessel Mykali be brought back from Athens to aid in the removal of the boulders.
From "Shipwrecked!" by Martin W. Sandler
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Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
