The Collaborative International Dictionary of English v.0.48:

Dissidence \Dis"si*dence\, n. [L. dissidentia: cf. F.
   dissidence. See Dissident, a.]
   Disagreement; dissent; separation from the established
   religion. --I. Taylor.
   [1913 Webster]

         It is the dissidence of dissent.         --Burke.
   [1913 Webster]

WordNet (r) 3.0 (2006):

dissidence
    n 1: disagreement; especially disagreement with the government

Moby Thesaurus II by Grady Ward, 1.0:

79 Moby Thesaurus words for "dissidence":
   aggressiveness, agreement to disagree, alienation, antagonism,
   apostasy, argumentation, bellicosity, belligerence, bickering,
   clashing, combativeness, conflict, contention, contentiousness,
   contradiction, controversy, counter-culture, difference, disaccord,
   disaccordance, disagreement, disapprobation, disapproval, discord,
   discordance, discordancy, discrepancy, disharmony, disparity,
   dissatisfaction, dissension, dissent, dissentience, dissonance,
   disunion, disunity, divergence, diversity, dropping out, faction,
   factiousness, flak, heterodoxy, inaccordance, inequality,
   infighting, irascibility, irritability, jarring, litigiousness,
   minority opinion, misbelief, negation, nonagreement, nonassent,
   nonconcurrence, nonconformism, nonconformity, nonconsent,
   opposition, oppugnancy, partisan spirit, partisanship, pugnacity,
   quarrelsomeness, recusance, recusancy, rejection, repudiation,
   repugnance, schism, secession, shrewishness, strife, underground,
   unharmoniousness, unorthodoxy, variance, withdrawal