Basalt Share definition Flag 1) A hard, black, often glassy, volcanic rock. It was produced by the partial melting of the Earth's mantle. 2) A stone-like, hard black unglazed pottery. 1) The statue was built on a basalt tower. 2) That vase cannot break, it's made of basalt. Basalt by Jafje July 11, 2007 0 0 Get merch Get the Basalt mug. Buy Now — $32.95 See more merch