1. Characteristic of, pertaining to, situated in or upon, formed in, or derived from volcanoes.
2. Discharged from or produced by volcanoes; such as, volcanic mud.
3. Characterized by the presence of volcanoes; a volcanic area.
4. Suggestive of or resembling a volcano; potentially explosive; volatile: "The mother had a volcanic reaction when her son knocked the vase and flowers off the table."

Pertaining to or produced by a pseudo-volcano.

Fine pyroclastic material.

The term usually refers to the unconsolidated material but sometimes is also used for its consolidated counterpart, tuff.

A water-deposited composite rock containing more than 50% volcanic material: A volcanic conglomerate consists particularly of coarse pyroclastics.

A steep-sided, rounded mass of viscous lava forming a dome-shaped or bulbous mass over a volcanic vent.

A seismic disturbance that is due to the direct action of volcanic forces or one whose origin lies under or near a volcano, whether active, dormant, or extinct.

A natural glass produced by the cooling of molten lava, or a liquid fraction of it, too rapidly to permit crystallization.

Examples are obsidian, pitchstone, tachylyte, and the glassy mesostasis of many extrusive rocks.

A mixture of water and volcanic ash formed either on land or at the time of eruption.

A mass of hardened volcanic magma that has been thrust upward into a volcanic cone by subterranean pressure, remaining upright after the surrounding material has been stripped away by erosion.