boulder
noun
a detached and rounded or worn rock, especially a large one.
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owlder.
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
Having squandered the good-will created by Sam Ryder's success, the BBC delegation now has the tricky task of pushing the boulder back up the hill.
From BBC ● May 17, 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
I will not let that boulder crush me.
From "Across So Many Seas" by Ruth Behar
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
Justice Clarence Thomas asked a lawyer representing Boulder.
From The Wall Street Journal ● Oct. 5, 2026
After what happened to Boulder and Maple—I know better, I know better...
From "Wayward Creatures" by Dayna Lorentz
Crews are installing boulders to separate the roadway from the waves.
From Los Angeles Times ● Oct. 24, 2026
By extending the calculations from individual particles to the much larger boulders found on Bennu, they were able to reproduce the low thermal inertia observed by the spacecraft.
From Science Daily ● Oct. 20, 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
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
The hills were strewn with boulders and stunted cedars, all shimmering in the hazy air.
From "The House of Hades" by Rick Riordan
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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.
