n. [ Icel. geysir, fr. geysa to rush furiously, fr. gjōsa to gush. Cf. Gush. ] A boiling spring which throws forth at frequent intervals jets of water, mud, etc., driven up by the expansive power of steam. [ 1913 Webster ]

☞ Geysers were first known in Iceland, and later in New Zealand. In the Yellowstone region in the United States they are numerous, and some of them very powerful, throwing jets of boiling water and steam to a height of 200 feet. They are grouped in several areas called geyser basins. The mineral matter, or geyserite, with which geyser water is charged, forms geyser cones about the orifice, often of great size and beauty. [ 1913 Webster ]

n. [ From Geyser. ] (Min.) A loose hydrated form of silica, a variety of opal, deposited in concretionary cauliflowerlike masses, around some hot springs and geysers. [ 1913 Webster ]