Definition of St. Helens, Mount in US English:

St. Helens, Mount

proper noun

  • An active volcano in southwestern Washington, in the Cascade Range, that rises to 8,312 feet (2,560 m). A dramatic eruption in May 1980 reduced its height by more than a thousand feet and spread volcanic ash and debris over a vast area. In late 2004, a massive extrusion of lava had geologists monitoring the possibility of another explosive eruption.