1. The quality or condition of being hardened.
2. The act or process of becoming hardened.
3. Pathology. The hardening of a normally soft tissue or organ, especially the skin, because of inflammation, infiltration of a neoplasm, or an accumulation of blood.

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.