A basic, dark-colored, holocrystalline, igneous rock, consisting essentially of a triclinic feldspar and pyroxene with magnetic iron; -- often limited to rocks pretertiary in age. It includes part of what was early called greenstone.
A common basic igneous rock usually occurring in dykes or sills.
A basic igneous rock mineralogically the same as basalt and gabbro, but coarser-grained than basalt and finer-grained than gabbro. The plagioclase forms lath-shaped crystals lying in all directions among irregular grains of augite, giving rise to a peculiar diabasic texture. Included in the general name of "trap."