The Collaborative International Dictionary of English v.0.48:

Resignation \Res`ig*na"tion\ (r[e^]z`[i^]g*n[=a]"sh[u^]n), n.
   [F. r['e]signation. See Resign.]
   1. The act of resigning or giving up, as a claim, possession,
      office, or the like; surrender; as, the resignation of a
      crown or commission.
      [1913 Webster]

   2. The state of being resigned or submissive; quiet or
      patient submission; unresisting acquiescence; as,
      resignation to the will and providence of God.
      [1913 Webster]

   Syn: Patience; surrender; relinquishment; forsaking;
        abandonment; abdication; renunciation; submission;
        acquiescence; endurance. See Patience.
        [1913 Webster]

WordNet (r) 3.0 (2006):

resignation
    n 1: acceptance of despair [syn: resignation, surrender]
    2: the act of giving up (a claim or office or possession etc.)
    3: a formal document giving notice of your intention to resign;
       "he submitted his resignation as of next month"

Moby Thesaurus II by Grady Ward, 1.0:

138 Moby Thesaurus words for "resignation":
   Quakerism, abandonment, abdication, abeyance, abjuration,
   abjurement, acceptance, acclimation, acclimatization, acedia,
   acquiescence, adaptation, adjustment, aloofness, amenability,
   apathy, assent, ataraxia, ataraxy, benumbedness, blah, blahs,
   capitulation, cessation, cession, cold storage, comatoseness,
   comfort, complaisance, compliance, composure, conformity, consent,
   content, contentedness, contentment, deference, desistance,
   detachment, discontinuance, disinterest, dispassion, dispensation,
   disposal, disposition, dropping out, dullness, dumping, ease,
   entire satisfaction, euphoria, forbearance, forgoing, forswearing,
   fulfillment, getting rid of, giving up, handing over, happiness,
   heartlessness, hebetude, homage, hopelessness, humbleness,
   humility, inappetence, indifference, insouciance, kneeling,
   lack of appetite, languidness, lethargicalness, lethargy,
   letting go, listlessness, long-suffering, longanimity, lowliness,
   meekness, modesty, nonchalance, nonexercise, nonopposal,
   nonopposition, nonresistance, nonviolent resistance, notice,
   numbness, obedience, obeisance, passive resistance, passiveness,
   passivity, patientness, peace of mind, phlegm, phlegmaticalness,
   phlegmaticness, plucklessness, quietism, recantation,
   reconcilement, reconciliation, release, relinquishment,
   renouncement, renunciation, resignedness, retraction, riddance,
   sacrifice, satisfaction, sloth, sluggishness, sopor,
   soporifousness, spiritlessness, spunklessness, stupefaction,
   stupor, subjection, submission, submissiveness, submittal,
   supineness, surrender, suspension, swearing off, torpidity,
   torpidness, torpor, uncomplainingness, unconcern, waiver,
   well-being, withdrawing, withdrawnness, yielding



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

RESIGNATION. The act of an officer by which he declines his office, and
renounces the further right to use it. It differs from abdication. (q.v.)
     2. As offices are held at the will of both parties, if the resignation
of a officer be not accepted, he remains in office. 4 Dev. R. 1.