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![geyser](/images/sized/images/uploads/sd/Geyser-266x150.jpg)
Geyser in Geysir, Iceland. Photo: Julien Carnot
geyser:
A natural, hot-water underground spring that frequently erupts with a stream of hot water and steam. Most geysers erupt irregularly. Other geysers, such as Old Faithful in Yellowstone National Park, erupt at fairly regular intervals. [Geyser was named for a hot spring in Iceland and means “gusher” in Icelandic.]