basalt

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A hard, dense, dark igneous rock composed chiefly of plagioclase feldspar, pyroxene, and olivine, and often having a glassy appearance.
• noun A kind of hard unglazed pottery.

from The Century Dictionary.

• noun Proposed as a field term, in petrography, for all dark-colored aphanitie, nonporphyritic (aphyric), igneous rocks.
• noun A volcanic rock occurring widely, and consisting of a triclinic feldspar, together with augite and magnetite or titaniferous iron.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Geol.) A rock of igneous origin, consisting of augite and triclinic feldspar, with grains of magnetic or titanic iron, and also bottle-green particles of olivine frequently disseminated.
• noun An imitation, in pottery, of natural basalt; a kind of black porcelain.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun mineralogy A hard mafic igneous rock of varied mineral content; volcanic in origin, it makes up much of the Earth's oceanic crust.
• noun A type of unglazed pottery.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the commonest type of solidified lava; a dense dark grey fine-grained igneous rock that is composed chiefly of plagioclase feldspar and pyroxene