ferric oxide

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

• noun A dark red compound, Fe₂O₃, occurring naturally as hematite ore and rust and used in pigments and metal polishes and on magnetic tapes.

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

• noun chemistry The chemical compound Fe2O3, iron oxide where iron has a valence of +3. IUPAC has deprecated this term in favor of iron(III) oxide.

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

• noun a red oxide of iron