Other forms: lavas
Lava is melted rock that has reached the surface: orange, slow, glowing, folding over itself as it moves. You have seen it on the news, a bright river creeping down a hillside towards a road.
Here is the rule learners get wrong. While it is still underground it is magma, and it becomes lava the moment it comes out. Lava is also the name of the black rock left behind once it cools, which is why you can walk across a lava field a century later. The phrases are lava flow, molten lava and lava lamp. And the childhood game, the floor is lava, is now the standard joke for anything you must not touch.
1nounlavaHot melted rock that flows out of a volcano.
“Lava poured down the slope and swallowed the fence in seconds.”
2noundarkThe dark rock that is left when this cools and hardens.
“The whole island is built on black lava.”
lava is molten rock from inside the earth.
Lava came into English from Italian, and into Italian from the Neapolitan and Sicilian word lava, which meant both the fire from the mountain and a downpour overflowing the streets. It probably goes back to Latin lābēs, "a fall, a collapse, a subsidence", alongside lābīna, "landslide". The old story that it comes from lavo, "to wash", is now discredited, however neatly it fits.
Latin
lābēs — a fall; a collapse; subsidence
Neapolitan and Sicilian
lava — lava; downpour overflowing the streets
English, today
lava
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 lavo (“to wash”) is now widely discredited, nor is there probably any relation with Arabic لابة (“black volcanic rock”). Alternatively, the Romance words are connected with oc-pro lavo, lauvo (“flat stone”), from a Vulgar Latin - source borrowed from a cel language such as cel-gau lawā, but ultimately of obscure origin; see Proto-Celtic līwos for details.
Etymology from Wiktionary, CC BY-SA