- The definition of a boulder is a large, smooth rock.
- When you build a retaining wall and use a large rock in the wall, this rock is an example of a boulder.
- A rock that has been detached from the earth by erosion or for other reasons and that is free to be moved about is an example of a boulder.
A boulder beside a tide pool.
boulder definition by Webster's New World
- any large rock worn smooth and round by weather and water
- Geol. such a rock larger than a cobblestone with a diameter of at least 256 mm (c. 10 in)
Origin: Middle English bulder, short for bulderston ; from Scandinavian as in Swedish bullersten, literally , noisy stone ; from bullra, to roar (akin to bellow) plush sten, stone
Origin: from the abundance of large rocks there
boulder definition by American Heritage Dictionary
Origin: Middle English bulder, of Scandinavian origin; see bhel-2 in Indo-European roots.