NOUN (2)

1. willful refusal to appear before a court or comply with a court order; can result in a finding of contempt of court;

2. obstinate rebelliousness and insubordination; resistance to authority;

The Collaborative International Dictionary of English v.0.48:

Contumacy \Con"tu*ma*cy\ (k[o^]n"t[-u]*m[.a]*s[y^]), n.; pl.
   Contumacies (k[o^]n"t[-u]*m[.a]*s[i^]z). [L. contumacia,
   fr. contumax, -acis, insolent; prob. akin to contemnere to
   despise: cf. F. contumace. Cf. Contemn.]
   1. Stubborn perverseness; pertinacious resistance to
      authority.
      [1913 Webster]

            The bishop commanded him . . . to be thrust into the
            stocks for his manifest and manifold contumacy.
                                                  --Strype.
      [1913 Webster]

   2. (Law) A willful contempt of, and disobedience to, any
      lawful summons, or to the rules and orders of court, as a
      refusal to appear in court when legally summoned.

   Syn: Stubbornness; perverseness; obstinacy.
        [1913 Webster]

WordNet (r) 3.0 (2006):

contumacy
    n 1: willful refusal to appear before a court or comply with a
         court order; can result in a finding of contempt of court
    2: obstinate rebelliousness and insubordination; resistance to
       authority

Bouvier's Law Dictionary, Revised 6th Ed (1856):

CONTUMACY, civil law. The refusal or neglect of a party accused to appear
and answer to a charge preferred against him in a court of justice. This
word is derived from the Latin contumacia, disobedience. 1 Bro. Civ. Law,
455; Ayl. Parer. 196; Dig. 50, 17, 52; Code Nap. art. 22.
     2. Contumacy is of two kinds, actual and presumed: actual contumacy is
when the party before the court refuses to obey some order of the court;
presumed contumacy is the act of refusing or declining to appear upon being
cited. 3 Curt. Ecc. R. 1.