harden
hard.en \'ha:rd-*n\ \'ha:rd-nin, -*n-in\ vb or hard.en.ing 1: to make hard or harder : INDURATE 2: to confirm in dispostion, feelings, or action; esp : to make ca llous {~ed his heart} 3: INURE, TOUGHEN {~ troops} 1: to become hard or harder 2a: to become confirmed or strengthened 2b: to assume an appearance of harshness or severity 3: to become higher or less subject to fluctuations downward