Pronunciation: (här'dn),[key] —v.t. 1. to make hard or harder: to harden steel. 2. to make pitiless or unfeeling: to harden one's heart. 3. to make rigid or unyielding; stiffen: The rigors of poverty hardened his personality. 4. to strengthen or confirm, esp. with reference to character, intentions, feelings, etc.; reinforce.
5. to make hardy, robust, or capable of endurance; toughen.
6. Mil.to reinforce the structure of (a military or strategic installation) to protect it from nuclear bombardment.
—v.i. 1. to become hard or harder.
2. to become pitiless or unfeeling.
3. to become rigid or unyielding; stiffen: His personality hardened over the years. 4. to become confirmed or strengthened: His resistance hardened. 5. to become inured or toughened: The troops hardened under constant fire. 6. Com.(of a market, prices, etc.)
a. to cease to fluctuate; firm: When the speculators withdrew from the market, the prices hardened. b. to rise higher.
Pronunciation: (här'dn),[key] —n. Sir Arthur, 1865–1940, English biochemist: Nobel prize 1929.