harden

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

• intransitive verb To make hard or harder.
• intransitive verb To enable to withstand physical or mental hardship.
• intransitive verb To make unfeeling, unsympathetic, or callous.
• intransitive verb To make fixed, settled, or less subject to change.
• intransitive verb To make less vulnerable to attack by surrounding with earth or concrete.
• intransitive verb To become hard or harder.
• intransitive verb To become fixed, settled, or less subject to change.
• intransitive verb To become inured.
• intransitive verb To take on a disapproving or severe appearance.
• intransitive verb To rise and become stable. Used of prices.

from The Century Dictionary.

• Of hards or inferior flax.
• noun Hards or inferior flax.
• noun A cloth of coarse fiber and texture, made from hards.
• To make hard or more hard in substance or texture; make firm or compact; indurate: as, to harden steel, clay, or tallow; to harden the hands or muscles by toil.
• To dry (clothes) by airing.
• To make hard or harder in feeling; strengthen or confirm with respect to any element of character; inure; toughen; especially, to make indifferent, unfeeling, obstinate, wicked, etc.
• Synonyms To accustom, discipline, train, toughen, habituate, steel, brace, nerve.
• To become hard or more hard; acquire solidity or compactness: as, mortar hardens in drying.
• To become inured or toughened; especially, to become unfeeling.
• To rise in price; grow dear: as, the market hardens.

from the GNU version of the Collaborative International Dictionary of English.

• transitive verb To make hard or harder; to make firm or compact; to indurate.
• transitive verb To accustom by labor or suffering to endure with constancy; to strengthen; to stiffen; to inure; also, to confirm in wickedness or shame; to make unimpressionable.
• intransitive verb To become hard or harder; to acquire solidity, or more compactness.
• intransitive verb To become confirmed or strengthened, in either a good or a bad sense.

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

• verb intransitive To become hard (tough, resistant to pressure).
• verb transitive, ergative To make something hard or harder (tough, resistant to pressure).
• verb transitive, dated To become or make a person or thing resistant or less sensitive.

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

• verb make fit
• verb cause to accept or become hardened to; habituate
• verb harden by reheating and cooling in oil
• verb become hard or harder
• verb make hard or harder