1Of or relating to iron; consisting of or containing iron. Occasionally: specifically (Chemistry) = "ferrous".
rare Resembling polished iron in appearance, metallic grey.
Mid 17th century; earliest use found in Thomas Browne (1605–1682), physician and author. From classical Latin ferreus made of iron, of or characteristic of iron, iron-barred, ironclad, having the nature of iron, hard-hearted, untiring, inexorable, shameless, brazen, in scientific Latin also resembling the colour of polished iron + -ous.