Old Faithful geyser.
Old Faithful definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
noted geyser in Yellowstone National Park, which erupts about every 67 minutes
Old Faithful definition by American Heritage Dictionary
A geyser in Yellowstone National Park in northwest Wyoming. Its eruptions, which last about 4 minutes, occur on the average of once every 65 minutes (the intervals can vary from 33 to 90 minutes). The geyser sends up a column of hot water and steam ranging from 35.4 to 53.4 m (116 to 175 ft) high.