- a vent in the earth's crust through which lava, steam, ashes, etc., are expelled, either continuously or at irregular intervals.
- a mountain or hill, usually having a cuplike crater at the summit, formed around such a vent from the ash and lava expelled through it.
- an opening in the earth's crust from which molten lava, rock fragments, ashes, dust, and gases are ejected from below the earth's surface
- a mountain formed from volcanic material ejected from a vent in a central crater
