WordWeb Online

1. Relating to or produced by or consisting of volcanoes
   "volcanic steam"; "volcanic islands such as Iceland"; "a volcanic cone is a conical mountain or hill built up of material from volcanic eruptions"
    
2. Explosively unstable
   "a volcanic temper"
    
3. Igneous rock produced by eruption and solidified on or near the earth's surface; rhyolite or andesite or basalt
   "volcanic rock includes the volcanic glass obsidian"

See also: extrusive, unstable, volcanically, volcano

Encyclopedia: Volcanic