Source : Webster's Revised Unabridged Dictionary (1913)

Volcanic \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.