Molten rock material on Earth’s surface. Lava is the molten material expelled by a volcano. It cools to form igneous rock. 1. Molten extrusive material that reaches the earth’s surface through volcanic vents and fissures. 2. The rock mass formed by consolidation of molten rock issuing from volcanic vents and fissures, consisting chiefly of magnesium silicate; used for insulators.
Related terms: