lava
n. uncountablen. hot, melted rock that comes out of a volcano. When it cools down, it turns into hard, solid rock.
n. molten rock expelled by a volcano during an eruption. Once cooled and solidified, it forms igneous rock.
The red lava flowed slowly down the side of the mountain.
Scientists monitored the speed of the lava as it moved toward the abandoned village.
The viscosity of the lava determines the shape of the volcano, with thinner flows creating broad shield volcanoes and thicker flows building steep, explosive peaks.
From Italian, from Neapolitan and Sicilian lava (“lava; downpour overflowing the streets”), likely from Latin lābēs (“a fall; a collapse; subsidence”); compare lābīna (“landslide”). A supposed relation with lavare (“to wash”) is now widely discredited, nor is there probably any relation with Arabic لابة (lāba, “black volcanic rock”). Alternatively, the Romance words are connected with Provençal lavo, lauvo (“flat stone”), from a Vulgar Latin source borrowed from a Celtic language such as Gaulish lawā, but ultimately of obscure origin; see Proto-Celtic līwos for details.
Uncountable when referring to the substance; countable when referring to specific types or distinct flows of the material.