The Collaborative International Dictionary of English v.0.48:

Renege \Re*nege"\ (r?-n?j" or r?-n?g"), v. t. [LL. renegare. See
   Renegade.]
   To deny; to disown. [Obs.] --Shak.
   [1913 Webster]

         All Europe high (all sorts of rights reneged)
         Against the truth and thee unholy leagued. --Sylvester.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Renege \Re*nege"\, v. i.
   1. To deny. [Obs.] --Shak.
      [1913 Webster]

   2. To fail to keep (a commitment or promise); -- often used
      with on; as, to renege on one's promise.
      [PJC]

   3. (Card Playing) To revoke; to play a card that cannot
      legally be played according to the rules. [R.]
      [1913 Webster +PJC]

WordNet (r) 3.0 (2006):

renege
    n 1: the mistake of not following suit when able to do so [syn:
         revoke, renege]
    v 1: fail to fulfill a promise or obligation; "She backed out of
         her promise" [syn: renege, renege on, renegue on, go
         back on]

Moby Thesaurus II by Grady Ward, 1.0:

78 Moby Thesaurus words for "renege":
   abandon, abjure, abolish, abrogate, annul, apostatize, back down,
   back out, backpedal, backwater, beg off, cancel, climb down,
   countermand, counterorder, crawfish out, cry off, default, defect,
   degenerate, deny, depart from, desert, disannul, disavow, discard,
   disclaim, disown, do away with, drop out, eat crow, eat humble pie,
   evacuate, forsake, forswear, go back on, invalidate, jettison,
   jilt, leave, leave behind, leave flat, make void, maroon, nullify,
   override, overrule, pull out, quit, quit cold, recall, recant,
   renegade, renounce, repeal, repudiate, rescind, resile, retract,
   reverse, revoke, say goodbye to, set aside, stand down, suspend,
   swallow, take back, take leave of, throw over, turn against,
   turn traitor, unsay, vacate, void, waive, welsh, withdraw,
   write off