The Collaborative International Dictionary of English v.0.48:

Harden \Hard"en\, v. i.
   1. To become hard or harder; to acquire solidity, or more
      compactness; as, mortar hardens by drying.
      [1913 Webster]

            The deliberate judgment of those who knew him [A.
            Lincoln] has hardened into tradition. --The Century.
      [1913 Webster]

   2. To become confirmed or strengthened, in either a good or a
      bad sense.
      [1913 Webster]

            They, hardened more by what might most reclaim.
                                                  --Milton.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Harden \Hard"en\ (h[aum]rd"'n), v. t. [imp. & p. p. Hardened
   (-'nd); p. pr. & vb. n. Hardening (-'n*[i^]ng).] [OE.
   hardnen, hardenen.]
   1. To make hard or harder; to make firm or compact; to
      indurate; as, to harden clay or iron.
      [1913 Webster]

   2. 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.
      "Harden not your heart." --Ps. xcv. 8.
      [1913 Webster]

            I would harden myself in sorrow.      --Job vi. 10.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Hurden \Hur"den\, n. [From Hurds.]
   A coarse kind of linen; -- called also harden. [Prov. Eng.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

harden
    v 1: become hard or harder; "The wax hardened" [syn: harden,
         indurate] [ant: soften]
    2: make hard or harder; "The cold hardened the butter" [syn:
       harden, indurate] [ant: soften]
    3: harden by reheating and cooling in oil; "temper steel" [syn:
       temper, harden]
    4: make fit; "This trip will season even the hardiest traveller"
       [syn: season, harden]
    5: cause to accept or become hardened to; habituate; "He was
       inured to the cold" [syn: inure, harden, indurate]