The Collaborative International Dictionary of English v.0.48:

Rebel \Re*bel"\ (r[-e]*b[e^]l"), v. i. [imp. & p. p. Rebelled
   (r[-e]*b[e^]ld); p. pr. & vb. n. Rebelling.] [F. rebeller,
   fr. L. rebellare to make war again; pref. re- again + bellare
   to make war, fr. bellum war. See Bellicose, and cf. Revel
   to carouse.]
   1. To renounce, and resist by force, the authority of the
      ruler or government to which one owes obedience. See
      Rebellion.
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            The murmur and the churls' rebelling. --Chaucer.
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            Ye have builded you an altar, that ye might rebel
            this day against the Lord.            --Josh. xxii.
                                                  16.
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   2. To be disobedient to authority; to assume a hostile or
      insubordinate attitude; to revolt.
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            How could my hand rebel against my heart?
            How could your heart rebel against your reason?
                                                  --Dryden.
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The Collaborative International Dictionary of English v.0.48:

Rebel \Reb"el\ (r[e^]b"[e^]l), a. [F. rebelle, fr. L. rebellis.
   See Rebel, v. i.]
   Pertaining to rebels or rebellion; acting in revolt;
   rebellious; as, rebel troops.
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         Whoso be rebel to my judgment.           --Chaucer.
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         Convict by flight, and rebel to all law. --Milton.
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The Collaborative International Dictionary of English v.0.48:

Rebel \Reb"el\, n. [F. rebelle.]
   One who rebels.
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   Syn: Revolter; insurgent.

   Usage: Rebel, Insurgent. Insurgent marks an early, and
          rebel a more advanced, stage of opposition to
          government. The former rises up against his rulers,
          the latter makes war upon them.
          [1913 Webster]

WordNet (r) 3.0 (2006):

Rebel
    n 1: `Johnny' was applied as a nickname for Confederate soldiers
         by the Federal soldiers in the American Civil War;
         `greyback' derived from their grey Confederate uniforms
         [syn: Rebel, Reb, Johnny Reb, Johnny, greyback]
    2: a person who takes part in an armed rebellion against the
       constituted authority (especially in the hope of improving
       conditions) [syn: insurgent, insurrectionist, freedom
       fighter, rebel]
    3: someone who exhibits great independence in thought and action
       [syn: maverick, rebel]
    v 1: take part in a rebellion; renounce a former allegiance
         [syn: rebel, arise, rise, rise up]
    2: break with established customs [syn: rebel, renegade]

The Devil's Dictionary (1881-1906):

REBEL, n.  A proponent of a new misrule who has failed to establish
it.