/ Dictionary / Index V volcanic glass: Meaning and Definition of Find definitions for: volcan'ic glass' Pronunciation: [key] a natural glass produced when molten lava cools very rapidly; obsidian. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. volcanic cone volcaniclastic Related Content Daily Word Quiz: clairvoyant Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language