boulder

noun

boul·​der ˈbōl-dər 

variants or less commonly bowlder

: a detached and rounded or much-worn mass of rock

bouldered

ˈbōl-dərd 

adjective

bouldery

ˈbōl-d(ə-)rē 

adjective

Examples of boulder in a Sentence

Recent Examples on the Web

The researchers said all the boulders and other debris flung off Dimorphos in the crash provided as much push to Dimorphos as the spacecraft itself — a doubling of momentum. —Marcia Dunn, Los Angeles Times, 9 Mar. 2026

About an hour's drive north of Dunedin on the South Island, Koekohe Beach is famous among geologists for the spherical boulders that formed about 65 million years ago. —Madeline Bilis, Travel + Leisure, 8 Mar. 2026

Inevitably, the boulder will roll backward, undoing decades and billions of dollars of work. —Philip Budge, The Conversation, 5 Mar. 2026

Sand Harbor State Park A hair under an hour from Reno, Lake Tahoe’s most photogenic shoreline features clear, turquoise water lapping against smooth granite boulders and an expansive, sandy beach seemingly flown in from Turks & Caicos. —Ted Alvarez, Outside, 3 Mar. 2026

Word History

Etymology

short for boulder stone, from Middle English bulder ston, partial translation of a word of Scandinavian origin; akin to Swedish dialect bullersten large stone in a stream, from buller noise + sten stone

First Known Use

1607, in the meaning defined above

Rhymes for boulder

• bolder
• bowlder
• colder
• folder
• golder
• holder
• molder
• moulder
• older
• polder
• shoulder
• beholder

Kids Definition

boulder

noun

boul·​der ˈbōl-dər 

: a large detached and rounded or worn mass of rock

Geographical Definition

Boulder

geographical name

Boul·​der ˈbōl-dər 

city northwest of Denver in north central Colorado population 97,385