Boulder Definition

bōldər

boulders

noun

boulders

Any large rock worn smooth and round by weather and water.

Webster's New World

Such a rock larger than a cobblestone with a diameter of at least 256 mm (c. 10 in)

Webster's New World

A large piece of stone that can theoretically be moved if enough force is applied.

Wiktionary

Synonyms:

verb

To engage in bouldering.

Wiktionary

Other Word Forms of Boulder

Singular:

boulder

Plural:

boulders

From Middle English bulder, possibly from Swedish bullersten (“noisy stone”), or possibly from Dutch bolder

From Wiktionary
Middle English bulder of Scandinavian origin bhel-² in Indo-European roots

From American Heritage Dictionary of the English Language, 5th Edition