Duration: Length of a geyser eruption.

Eruption: The ejection of water from a geyser, synonym for "play".

Fountain Geyser: A geyser erupting with relatively explosive bursts of water, generally issuing from pools with large vents or craters.

Geyser: A hot spring that periodically ejects water some height above the surrounding surface.

Hot Spring: Any spring whose water is above the ambient air temperature. Conventially, in the United States, the spring should be at least 15 degrees Fahrenheit over the mean annual temperature of the air in their localities.

Interval: The amount of time between the end of an eruption and the beginning of the next consecutive eruption.

Period: Interval plus duration. Length of time from the beginning of an eruption to the beginning of the next consecutive eruption.

Perpetual Spouter: A hot spring with continuous spouting activity.

Siliceous Sinter: Porous opaline silica, precipitated as an encrustation by a geyser or hot spring, a synonym for "geyserite"..

Vent: The surface geyser opening. The point at the surface which water exits the geyser.