The Collaborative International Dictionary of English v.0.48:

Oblivious \Ob*liv"i*ous\, a. [L. obliviosus: cf. F. oblivieux.]
   [1913 Webster]
   1. Promoting oblivion; causing forgetfulness. "The oblivious
      pool." --Milton.
      [1913 Webster]

            She lay in deep, oblivious slumber.   --Longfellow.
      [1913 Webster]

   2. Evincing oblivion; forgetful.
      [1913 Webster]

            Through are both weak in body and oblivious.
                                                  --Latimer.
      [1913 Webster] -- Obliv"i*ous*ly, adv. --
      Ob*liv"i*ous*ness, n. --Foxe.
      [1913 Webster]

WordNet (r) 3.0 (2006):

oblivious
    adj 1: (followed by `to' or `of') lacking conscious awareness
           of; "oblivious of the mounting pressures for political
           reform"; "oblivious to the risks she ran"; "not unmindful
           of the heavy responsibility" [syn: oblivious(p),
           unmindful(p)]
    2: failing to keep in mind; "forgetful of her responsibilities";
       "oblivious old age" [syn: forgetful, oblivious]

Moby Thesaurus II by Grady Ward, 1.0:

148 Moby Thesaurus words for "oblivious":
   Lethean, absent, absent-minded, absentminded, absorbed, abstracted,
   airy, amnestic, asleep, bemused, blank, blankminded, blind,
   blind to, blocked, calm, careless, castle-building, casual,
   cataleptic, catatonic, cold, comatose, converted, cursory,
   daydreaming, daydreamy, dead, dead asleep, dead to, deaf, deaf to,
   deep asleep, degage, detached, disregardant, disregardful, distant,
   doped, dormant, dreaming, dreamy, drowsing, drugged, easygoing,
   ecstatic, elsewhere, empty, empty-headed, engrossed, faraway,
   fast asleep, fatuous, flaked-out, flippant, forgetful, forgetting,
   free and easy, half-awake, half-conscious, heedless, in a reverie,
   in the clouds, inane, inclined to forget, incogitant, incognizant,
   inconsiderate, indifferent, insensible, insensitive, insouciant,
   lazy, lost, lost in thought, lost to, meditative, mooning,
   moonraking, museful, musing, napping, narcotized, nirvanic,
   nodding, offhand, out, out cold, out of it, passive, pensive,
   perfunctory, pipe-dreaming, preoccupied, quietistic, rapt,
   reckless, regardless, relaxed, removed, repressed, respectless,
   semiconscious, senseless, sleeping, slumbering, somewhere else,
   sound asleep, spaced out, stargazing, stoned, strung out,
   suppressed, tactless, taken up, thoughtfree, thoughtless, tranquil,
   transported, unacquainted, unaware, unconcerned, unconscious,
   undiplomatic, unfamiliar, unfeeling, unheedful, unheeding,
   unideaed, uninformed, uninstructed, unintellectual, unknowing,
   unmindful, unoccupied, unprepared, unready, unreasoning,
   unsolicitous, untactful, unthinking, unwitting, vacant, vacuous,
   woolgathering, wrapped in thought, zonked, zonked out