The Collaborative International Dictionary of English v.0.48:

Oblivion \Ob*liv"i*on\, n. [L. oblivio, akin to oblivisci to
   forget: cf. OF. oblivion.]
   1. The act of forgetting, or the state of being forgotten;
      cessation of remembrance; forgetfulness.
      [1913 Webster]

            Second childishness and mere oblivion. --Shak.
      [1913 Webster]

            Among our crimes oblivion may be set. --Dryden
      [1913 Webster]

            The origin of our city will be buried in eternal
            oblivion.                             --W. Irving.
      [1913 Webster]

   2. Official ignoring of offenses; amnesty, or general pardon;
      as, an act of oblivion. --Sir J. Davies.
      [1913 Webster]

   Syn: See Forgetfulness.
        [1913 Webster]

WordNet (r) 3.0 (2006):

oblivion
    n 1: the state of being disregarded or forgotten [syn:
         oblivion, limbo]
    2: total forgetfulness; "he sought the great oblivion of sleep"
       [syn: obliviousness, oblivion]

Moby Thesaurus II by Grady Ward, 1.0:

95 Moby Thesaurus words for "oblivion":
   KO, Lethe, abandon, absentmindedness, anonymity, blackness,
   blackout, blank mind, blankmindedness, blankness, calm of mind,
   careless abandon, carelessness, casualness, catalepsy, catatonia,
   catatony, coma, cursoriness, darkness, decay of memory, disregard,
   disregardfulness, easiness, emptiness of mind, empty-headedness,
   extinction, faint, fallow mind, fatuity, foolishness,
   forgetfulness, forgetting, forgiveness, grayout, hastiness,
   hazy recollection, heedlessness, inanity, inconsiderateness,
   inconsideration, indifference, insensibility, insensibleness,
   insouciance, kayo, knockout, lack of foresight, laziness, lethe,
   limbo, lipothymia, lipothymy, mental blankness, nepenthe, nihility,
   nirvana, nirvana principle, nothingness, obliteration,
   obliviousness, obscurity, offhandedness, passivity,
   perfunctoriness, quietism, recklessness, regardlessness,
   semiconsciousness, senselessness, short memory, sleep, sprezzatura,
   stupor, swoon, syncope, tabula rasa, tactlessness, thoughtfreeness,
   thoughtlessness, tranquillity, unawareness, unconsciousness,
   unheedfulness, unintelligence, unmindfulness, unpreparedness,
   unreadiness, unsolicitousness, unsolicitude, unthinkingness,
   vacancy, vacuity, void, waters of oblivion



The Devil's Dictionary (1881-1906):

OBLIVION, n.  The state or condition in which the wicked cease from
struggling and the dreary are at rest.  Fame's eternal dumping ground.
Cold storage for high hopes.  A place where ambitious authors meet
their works without pride and their betters without envy.  A dormitory
without an alarm clock.