Physical Geography. A hill, mountain, or other feature, typically conical in form, that is built up of solidified lava and rock debris and has a crater or vent through which, in periods of activity, molten rock (lava), rock fragments, steam, and gas are emitted from within the planet’s crust; (in early use also) †the crater or vent of such a mountain, etc. (obsolete).——Oxford English Dictionary

volcano:a mountain with a large hole at the top, through which lava (=very hot liquid rock) is sometimes forced out.—Longman Dictionary of Contemporary English  @en