\Vol*can"ic\, a. [Cf. F. volcanique, It. vulcanico.]
1. Of or pertaining to a volcano or volcanoes; as, volcanic
   heat.
2. Produced by a volcano, or, more generally, by igneous
   agencies; as, volcanic tufa.
3. Changed or affected by the heat of a volcano.
{Volcanic bomb}, a mass ejected from a volcano, often of
   molten lava having a rounded form.
{Volcanic cone}, a hill, conical in form, built up of
   cinders, tufa, or lava, during volcanic eruptions.
{Volcanic foci}, the subterranean centers of volcanic action;
   the points beneath volcanoes where the causes producing
   volcanic phenomena are most active.
{Volcanic glass}, the vitreous form of lava, produced by
   sudden cooling; obsidian. See {Obsidian}.
{Volcanic mud}, fetid, sulphurous mud discharged by a
   volcano.
{Volcanic rocks}, rocks which have been produced from the
   discharges of volcanic matter, as the various kinds of
   basalt, trachyte, scoria, obsidian, etc., whether compact,
   scoriaceous, or vitreous.