The Collaborative International Dictionary of English v.0.48:

Renunciation \Re*nun`ci*a"tion\ (r?-n?n`s?-?"sh?n or
   -sh?-?"sh?n; 277), n. [Cf. F. renonciation, L. renuntiatio
   ann announcement. See Renounce.]
   1. The act of renouncing.
      [1913 Webster]

   2. (Law) Formal declination to take out letters of
      administration, or to assume an office, privilege, or
      right.
      [1913 Webster]

   Syn: Renouncement; disownment; disavowal; disavowment;
        disclaimer; rejection; abjuration; recantation; denial;
        abandonment; relinquishment.
        [1913 Webster]

WordNet (r) 3.0 (2006):

renunciation
    n 1: rejecting or disowning or disclaiming as invalid;
         "Congressional repudiation of the treaty that the President
         had negotiated" [syn: repudiation, renunciation]
    2: the state of having rejected your religious beliefs or your
       political party or a cause (often in favor of opposing
       beliefs or causes) [syn: apostasy, renunciation,
       defection]
    3: an act (spoken or written) declaring that something is
       surrendered or disowned [syn: renunciation, renouncement]
    4: the act of renouncing; sacrificing or giving up or
       surrendering (a possession or right or title or privilege
       etc.) [syn: renunciation, forgoing, forswearing]

Moby Thesaurus II by Grady Ward, 1.0:

118 Moby Thesaurus words for "renunciation":
   abandonment, abdication, abeyance, abjuration, abjurement,
   abnegation, abrogation, absolute contradiction, annulment,
   apostasy, breakoff, capitulation, cease, ceasing, cessation,
   cession, close, closing, cold storage, constraint, contradiction,
   contrary assertion, contravention, controversion, countering,
   crossing, crossing-over, defection, degeneration, denial,
   desertion, desinence, desistance, disaffirmation, disallowance,
   disavowal, disclaimer, disclamation, discontinuance,
   discontinuation, disowning, disownment, dispensation, disposal,
   disposition, disproof, dropping out, dumping, eschewing,
   expatriation, forbearance, forbearing, forgoing, forswearing,
   frugality, gainsaying, getting rid of, giving in, giving over,
   giving up, golden mean, handing over, impugnment, letting go,
   moderateness, moderation, nonexercise, nothing in excess,
   nullification, palinode, palinody, recantation, recedence,
   recession, refutation, rejection, release, relinquishment,
   reneging, renouncement, reoccupy, repossess, repudiation,
   resignation, restraint, retake, retractation, retraction, retreat,
   revocation, revokement, riddance, sacrifice, self-abnegation,
   self-control, self-denial, self-discipline, self-mastery,
   self-restraint, self-sacrifice, shutdown, soberness, sobriety,
   sophrosyne, stopping, surcease, surrender, suspension,
   swearing off, temperance, temperateness, termination, treason,
   unsaying, waiver, withdrawal, withdrawing, yielding



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

RENUNCIATION. The act of giving up a right.
     2. It is a rule of law that any one may renounce a right which the law
has established in his favor. To this maxim there are many limitations. A
party may always renounce an acquired right; as, for example, to take lands
by descent; but one cannot always give up a future right, before it has
accrued, nor to the benefit conferred by law, although such advantage may be
introduced only for the benefit of individuals.
     3. For example, the power of making a will; the right of annulling a
future contract, on the ground of fraud; and the right of pleading the act
of limitations, cannot be renounced. The first, because the party must be
left free to make a will or not; and the latter two, because the right has
not yet accrued.
     4. This term is usually employed to signify the abdication or giving up
of one's country at the time of choosing another. The act of congress
requires from a foreigner who applies to become naturalized a renunciation
of all allegiance and fidelity to any foreign prince, potentate, state or
sovereignty, whereof such alien may, at the time, be a citizen or subject.
See Citizen; Expatriation; Naturalization; To renounce.