The Collaborative International Dictionary of English v.0.48:

Waiver \Waiv"er\, n. (Law)
   The act of waiving, or not insisting on, some right, claim,
   or privilege.
   [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

96 Moby Thesaurus words for "waiver":
   OK, abandonment, abdication, abeyance, abjuration, abjurement,
   abolishment, abolition, abrogation, admission, allowance,
   annulment, cancel, canceling, cancellation, cassation, cessation,
   cession, charter, circumscription, cold storage, concession,
   consent, countermand, counterorder, deed of release, defeasance,
   desistance, discontinuance, dispensation, dropping out, exception,
   exemption, extenuating circumstances, forbearance, forswearing,
   grain of salt, grant, handing over, hedge, hedging, invalidation,
   leave, liberty, license, limitation, mental reservation,
   modification, nonexercise, nullification, okay, patent, permission,
   permission to enter, qualification, quitclaim, recall, recantation,
   release, relinquishment, renege, renouncement, renunciation,
   repeal, rescinding, rescindment, rescission, reservation,
   resignation, restriction, retraction, reversal, revocation, revoke,
   revokement, salvo, setting aside, special case, special permission,
   special treatment, specialness, specification, surrender,
   suspension, ticket, ticket of admission, vacation, vacatur,
   voidance, voiding, vouchsafement, waiving, withdrawal, withdrawing,
   write-off, yielding