The Collaborative International Dictionary of English v.0.48:

Defiance \De*fi"ance\, n. [OF. defiance, desfiance, challenge,
   fr. desfier to challenge, F. d['e]fier. See Defy.]
   1. The act of defying, putting in opposition, or provoking to
      combat; a challenge; a provocation; a summons to combat.
      [1913 Webster]

            A war without a just defiance made.   --Dryden.
      [1913 Webster]

            Stood for her cause, and flung defiance down.
                                                  --Tennyson.
      [1913 Webster]

   2. A state of opposition; willingness to flight; disposition
      to resist; contempt of opposition.
      [1913 Webster]

            He breathed defiance to my ears.      --Shak.
      [1913 Webster]

   3. A casting aside; renunciation; rejection. [Obs.] "Defiance
      to thy kindness." --Ford.
      [1913 Webster]

   To bid defiance, To set at defiance, to defy; to
      disregard recklessly or contemptuously. --Locke.
      [1913 Webster]

WordNet (r) 3.0 (2006):

defiance
    n 1: intentionally contemptuous behavior or attitude [syn:
         defiance, rebelliousness]
    2: a hostile challenge
    3: a defiant act

Moby Thesaurus II by Grady Ward, 1.0:

88 Moby Thesaurus words for "defiance":
   audacity, boldness, bravado, brazenness, call, cartel, challenge,
   combative reaction, command, complaint, contempt, contrariness,
   contumaciousness, contumacy, counteraction, dare,
   declaration of war, defi, defiance of authority, defy, demur,
   despite, dispute, dissent, dissentience, effrontery, factiousness,
   fractiousness, hardihood, headstrongness, impudence,
   incorrigibility, indocility, indomitability, insolence,
   insubordination, insuppressibility, insurgency, intractability,
   intractableness, irrepressibility, muster, negativism,
   noncooperation, objection, obstinacy, obstreperousness, opposition,
   order, orneriness, passive resistance, perversity, protest,
   reaction, rebelliousness, rebuff, recalcitrance, recalcitrancy,
   recalcitration, refractoriness, reluctance, remonstrance,
   renitence, renitency, repellence, repellency, repulse, repulsion,
   resistance, restiveness, revolt, shrewishness, stand, stubbornness,
   stump, summons, temerity, uncontrollability, uncooperativeness,
   ungovernability, unmalleability, unmanageability, unmoldableness,
   unruliness, unsubmissiveness, untamableness, wildness,
   withstanding



U.S. Gazetteer Counties (2000):

Defiance -- U.S. County in Ohio
   Population (2000):    39500
   Housing Units (2000): 16040
   Land area (2000):     411.158299 sq. miles (1064.895060 sq. km)
   Water area (2000):    3.027456 sq. miles (7.841076 sq. km)
   Total area (2000):    414.185755 sq. miles (1072.736136 sq. km)
   Located within:       Ohio (OH), FIPS 39
   Location:             41.304320 N, 84.462745 W
   Headwords:
    Defiance
    Defiance, OH
    Defiance County
    Defiance County, OH


U.S. Gazetteer Places (2000):

Defiance, OH -- U.S. city in Ohio
   Population (2000):    16465
   Housing Units (2000): 7061
   Land area (2000):     10.538139 sq. miles (27.293653 sq. km)
   Water area (2000):    0.488358 sq. miles (1.264841 sq. km)
   Total area (2000):    11.026497 sq. miles (28.558494 sq. km)
   FIPS code:            21308
   Located within:       Ohio (OH), FIPS 39
   Location:             41.281891 N, 84.362856 W
   ZIP Codes (1990):     43512
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Defiance, OH
    Defiance


U.S. Gazetteer Places (2000):

Defiance, IA -- U.S. city in Iowa
   Population (2000):    346
   Housing Units (2000): 131
   Land area (2000):     0.398193 sq. miles (1.031314 sq. km)
   Water area (2000):    0.000000 sq. miles (0.000000 sq. km)
   Total area (2000):    0.398193 sq. miles (1.031314 sq. km)
   FIPS code:            19585
   Located within:       Iowa (IA), FIPS 19
   Location:             41.824740 N, 95.342056 W
   ZIP Codes (1990):
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Defiance, IA
    Defiance