The Collaborative International Dictionary of English v.0.48:

Rebellion \Re*bel"lion\ (r[-e]*b[e^]l"y[u^]n), n. [F.
   r['e]bellion, L. rebellio. See Rebel, v. i. Among the
   Romans rebellion was originally a revolt or open resistance
   to their government by nations that had been subdued in war.
   It was a renewed war.]
   1. The act of rebelling; open and avowed renunciation of the
      authority of the government to which one owes obedience,
      and resistance to its officers and laws, either by levying
      war, or by aiding others to do so; an organized uprising
      of subjects for the purpose of coercing or overthrowing
      their lawful ruler or government by force; revolt;
      insurrection.
      [1913 Webster]

            No sooner is the standard of rebellion displayed
            than men of desperate principles resort to it.
                                                  --Ames.
      [1913 Webster]

   2. Open resistance to, or defiance of, lawful authority.
      [1913 Webster]

   Commission of rebellion (Eng. Law), a process of contempt
      issued on the nonappearance of a defendant, -- now
      abolished. --Wharton. --Burrill.
      [1913 Webster]

   Syn: Insurrection; sedition; revolt; mutiny; resistance;
        contumacy. See Insurrection.
        [1913 Webster]

WordNet (r) 3.0 (2006):

rebellion
    n 1: refusal to accept some authority or code or convention;
         "each generation must have its own rebellion"; "his body
         was in rebellion against fatigue"
    2: organized opposition to authority; a conflict in which one
       faction tries to wrest control from another [syn:
       rebellion, insurrection, revolt, rising, uprising]

Moby Thesaurus II by Grady Ward, 1.0:

46 Moby Thesaurus words for "rebellion":
   anarchism, anarcho-syndicalism, anarchy, antinomianism, chaos,
   civil disorder, confusion, contumacy, criminal syndicalism,
   defiance, disobedience, disorder, disorderliness, disorganization,
   disruption, emeute, general uprising, insubordination, insurgence,
   insurgency, insurrection, jacquerie, levee en masse, lynch law,
   misrule, mob law, mob rule, mobocracy, mutiny, nihilism,
   ochlocracy, outbreak, peasant revolt, primal chaos, putsch,
   rebelliousness, resistance, revolt, revolution, riot, rising,
   syndicalism, tohubohu, turmoil, unruliness, uprising



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

REBELLION, crim. law. The taking up arms traitorously against the government
and in another, and perhaps a more correct sense, rebellion signifies the
forcible opposition and resistance to the laws and process lawfully issued.
     2. If the rebellion amount to treason, it is punished by the laws of
the United States with death. If it be a mere resistance of process, it is
generally punished by fine and imprisonment. See Dalloz, Dict. h.t.; Code
Penal, 209.



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

REBELLION, COMMISSION OF. A commission of rebellion is the name of a writ
issuing out of chancery to compel the defendant to appear. Vide Commission
of Rebellion.