volcanic glass

1. 1.

   a kind of natural glass produced when molten lava cools very rapidly

   Broadervolcanic rock

   Narrowerobsidianpitchstonetachylite

Questions about volcanic glass

What does volcanic glass mean?

volcanic glass means "a kind of natural glass produced when molten lava cools very rapidly".

Is volcanic glass a common word?

volcanic glass is banded "Rare" — specialist or archaic — most readers will not have met it. The band comes from how often the word appears in a large corpus of everyday English, not from an editor's impression.