​BOULDER (short for “boulder-stone,” of uncertain origin; cf. Swed. bullersten, a large stone which causes a noise of rippling water in a stream, from bullra, to make a loud noise), a large stone, weathered or water-worn; especially a geological term for a large mass of rock transported to a distance from the formation to which it belongs. Similarly, in mining, a mass of ore found at a distance from the lode.