The Collaborative International Dictionary of English v.0.48:

Oversight \O"ver*sight`\, n.
   1. Watchful care; superintendence; general supervision.
      [1913 Webster]

   2. An overlooking; an omission; an error. --Hooker.
      [1913 Webster]

   3. Escape from an overlooked peril. [R.] "His fool-happy
      oversight." --Spenser.
      [1913 Webster]

   Syn: Superintendence; supervision; inspection; overlooking;
        inadvertence; neglect; mistake; error; omission.
        [1913 Webster]

WordNet (r) 3.0 (2006):

oversight
    n 1: an unintentional omission resulting from failure to notice
         something [syn: oversight, inadvertence]
    2: management by overseeing the performance or operation of a
       person or group [syn: supervision, supervising,
       superintendence, oversight]
    3: a mistake resulting from inattention [syn: oversight,
       lapse]

Moby Thesaurus II by Grady Ward, 1.0:

132 Moby Thesaurus words for "oversight":
   accountability, administration, aegis, auspices, balk, bevue,
   blank, blunder, bossing, care, carelessness, charge, chasm, check,
   civil government, conduct, control, culpa, culpable negligence,
   cure, custodianship, custody, default, delinquency, dereliction,
   direction, discipline, disconformity, dispensation, disposition,
   disregard, empery, empire, error, eye, failure, false move,
   false step, fault, form of government, governance, government,
   guard, guardianship, guidance, handling, hands, heedlessness,
   inadvertence, inadvertency, inattention, inobservance, intendance,
   jurisdiction, keeping, laches, laissez-faire, lapse, lapsus calami,
   lapsus linguae, laxity, laxness, loose thread, looseness,
   maintenance, management, ministry, miscue, misstep, mistake,
   neglect, neglectfulness, negligence, nonadherence, noncompliance,
   nonconformance, nonconformity, nonfeasance, nonfulfillment,
   noninterference, nonobservance, nonperformance, nonrestriction,
   omission, overlook, overlooking, pastorage, pastorate, pastorship,
   patronage, permissiveness, political organization, polity,
   poor stewardship, preterition, procrastination, protection,
   protectorship, regime, regimen, regnancy, regulation, reign,
   remissness, responsibility, rule, running, safe hands, skip,
   slackness, slight, slip, slipup, sovereignty, stewardship, stumble,
   superintendence, superintendency, supervision, surveillance, sway,
   system of government, trip, tutelage, unobservance, unrigorousness,
   ward, wardenship, wardship, watch and ward, wing, wrong step