The American Heritage® Dictionary of the English Language, 4th Edition
n. An iron-containing protein complex, found principally in the intestinal mucosa, spleen, and liver, that functions as the primary form of iron storage in the body.
n. Any of a family of iron-carrying globular protein complexes consisting of 24 protein subunits.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. a protein containing 20% iron that is found in the intestines and liver and spleen; it is one of the chief forms in which iron is stored in the body
Word Usage
"Your doctor also may check the level of iron in your blood (this is called your serum iron) and the amount of iron that your body is storing (this form of iron is called ferritin)."