Source : Webster's Revised Unabridged Dictionary (1913)

Geyser \Gey"ser\, n. [Icel. geysir, fr. geysa to rush furiously,
   fr. gj[=o]sa 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.

   Note: 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.

Source : WordNet®

geyser
     n : a spring that discharges hot water and steam
     v : to overflow like a geyser