The Collaborative International Dictionary of English v.0.48:

Dissent \Dis*sent"\, v. i. [imp. & p. p. Dissented; p. pr. &
   vb. n. Dissenting.] [L. dissentire, dissentum; dis- +
   sentire to feel, think. See Sense.]
   1. To differ in opinion; to be of unlike or contrary
      sentiment; to disagree; -- followed by from.
      [1913 Webster]

            The bill passed . . . without a dissenting voice.
                                                  --Hallam.
      [1913 Webster]

            Opinions in which multitudes of men dissent from us.
                                                  --Addison.
      [1913 Webster]

   2. (Eccl.) To differ from an established church in regard to
      doctrines, rites, or government.
      [1913 Webster]

   3. To differ; to be of a contrary nature. --Hooker.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

dissenting \dissenting\ adj.
   disagreeing, especially with a majority.

   Syn: dissentient, dissident.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

dissenting
    adj 1: disagreeing, especially with a majority [syn:
           dissentient, dissenting(a), dissident]

Moby Thesaurus II by Grady Ward, 1.0:

72 Moby Thesaurus words for "dissenting":
   against, alienated, antiestablishment, at odds with,
   at variance with, breakaway, complaining, con, contrary,
   counter-culture, deviant, differing, disagreeing, disappointed,
   disapprobatory, disapproving, discontented, disenchanted,
   disgruntled, disillusioned, displeased, disputatious, disputing,
   dissatisfied, dissentient, dissident, fractious, in opposition,
   indignant, low, nonconformable, nonconforming, noncooperative,
   nonobservant, objecting, obstructive, on the barricades, opposed,
   opposing, poor, proof against, protesting, rebellious,
   recalcitrant, recusant, refractory, reluctant, renitent, repellent,
   resistant, resisting, resistive, retardant, retardative, sectarian,
   sectary, turned-off, unadaptable, unadjustable, unappreciative,
   unapproving, uncompliant, uncomplimentary, unconforming,
   uncooperative, underground, unfavorable, unhappy, unsubmissive,
   unyielding, up in arms, withstanding