The Collaborative International Dictionary of English v.0.48:

Dereliction \Der`e*lic"tion\, n. [L. derelictio.]
   1. The act of leaving with an intention not to reclaim or
      resume; an utter forsaking abandonment.
      [1913 Webster]

            Cession or dereliction, actual or tacit, of other
            powers.                               --Burke.
      [1913 Webster]

   2. A neglect or omission as if by willful abandonment.
      [1913 Webster]

            A total dereliction of military duties. --Sir W.
                                                  Scott.
      [1913 Webster]

   3. The state of being left or abandoned.
      [1913 Webster]

   4. (Law) A retiring of the sea, occasioning a change of
      high-water mark, whereby land is gained.
      [1913 Webster]

WordNet (r) 3.0 (2006):

dereliction
    n 1: a tendency to be negligent and uncaring; "he inherited his
         delinquency from his father"; "his derelictions were not
         really intended as crimes"; "his adolescent protest
         consisted of willful neglect of all his responsibilities"
         [syn: delinquency, dereliction, willful neglect]
    2: willful negligence

Moby Thesaurus II by Grady Ward, 1.0:

119 Moby Thesaurus words for "dereliction":
   Punic faith, abuse, apostasy, atrocity, bad faith, barratry,
   betrayal, bolt, breach, breach of faith, breach of promise,
   breach of trust, breakaway, crime, crime against humanity, culpa,
   culpable negligence, deadly sin, default, defection, delinquency,
   deserter, desertion, disaffection, disconformity, disloyalty,
   disregard, enormity, error, evil, failure, faithlessness,
   falseness, falsity, fault, felony, fickleness, genocide,
   guilty act, heavy sin, impropriety, inadvertence, inadvertency,
   inattention, inconstancy, indiscretion, inexpiable sin, infidelity,
   iniquity, injury, injustice, inobservance, laches, laissez-faire,
   lapse, laxity, laxness, looseness, mala fides, malefaction,
   malfeasance, malum, minor wrong, misdeed, misdemeanor, misfeasance,
   misuse, mortal sin, neglect, neglectfulness, negligence,
   nonadherence, noncompliance, nonconformance, nonconformity,
   nonfeasance, nonfulfillment, noninterference, nonobservance,
   nonperformance, nonrestriction, offense, omission, outrage,
   overlooking, oversight, peccadillo, peccancy, permissiveness,
   poor stewardship, procrastination, ratting, recreancy, remissness,
   schism, secession, sin, sin of commission, sin of omission,
   sinful act, slackness, slight, slip, tort, transgression, trespass,
   trip, trothlessness, unfaith, unfaithfulness, unloyalty,
   unobservance, unrigorousness, unsteadfastness, untrueness,
   unutterable sin, venial sin, walkout, wrong