The Collaborative International Dictionary of English v.0.48:

Disownment \Dis*own"ment\, n.
   Act of disowning. [R.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

disownment
    n 1: refusal to acknowledge as one's own [syn: disownment,
         disowning]

Moby Thesaurus II by Grady Ward, 1.0:

78 Moby Thesaurus words for "disownment":
   abjuration, abjurement, abrogation, absolute contradiction,
   annulment, chucking, chucking out, contempt, contradiction,
   contrary assertion, contravention, controversion, countering,
   crossing, declination, declining, denial, despisal, despising,
   disaffirmation, disallowance, disapproval, disavowal, discard,
   disclaimer, disclamation, discounting, disendowment, disherison,
   disinheritance, dismissal, disowning, dispossession, disproof,
   disregard, disseisin, eviction, exception, exclusion, expatriation,
   expropriation, foreclosure, forswearing, gainsaying, ignoring,
   impugnment, nonacceptance, nonapproval, nonconsideration,
   nullification, palinode, palinody, passing by, putting away,
   putting out, rebuff, recantation, reclaiming, refusal, refutation,
   rejection, reneging, renouncement, renunciation, repossessing,
   repossession, repudiation, repulse, retractation, retraction,
   revocation, revokement, scouting, spurning, throwing out,
   turning out, unsaying, withdrawal