boulder

n. large rounded rock

n. city in Colorado (USA)

In geology, a boulder is a rock with grain size of usually no less than 256 mm (10 inches) diameter. While a boulder may be small enough to move or roll manually, others are extremely massive. In common usage, a boulder is too large for a person to move. Smaller boulders are usually just called rocks or stones. The word boulder comes from Middle English "bulder" which was probably of Scandinavian origin such as dialectal Swedish "bullersten" meaning "noisy stone" (Imagine a large stone in a stream, causing water to roar around it) from "bullra" (to roar, cf. Dutch "bulderen", with the same meaning) and "steen" (stone).
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Noun
1. a town in north central Colorado; Rocky Mountains resort center and university town
(hypernym) town
(part-holonym) Colorado, Centennial State, CO

Noun
1. a large smooth mass of rock detached from its place of origin
(synonym) bowlder
(hypernym) rock, stone
(hyponym) Plymouth Rock

(n.)
Same as Bowlder.
  

(n.)
A mass of any rock, whether rounded or not, that has been transported by natural agencies from its native bed. See Drift.
  

(n.)
A large stone, worn smooth or rounded by the action of water; a large pebble.
  

     doubler