from The American Heritage® Dictionary of the English Language, 4th Edition
- adj. Containing or relating to a group of dark-colored minerals, composed chiefly of magnesium and iron, that occur in igneous rocks.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. Describing rocks, such as silicate minerals, magmas, and volcanic and intrusive igneous rocks, which contain relatively high concentrations of magnesium and iron.
- n. A rock with such properties.
ma(gnesium) + Latin f(errum), iron + -ic.(American Heritage® Dictionary of the English Language, Fourth Edition)
Blend of magnesium and ferric. (Wiktionary)