The Collaborative International Dictionary of English v.0.48:

Obliterate \Ob*lit"er*ate\, v. t. [imp. & p. p. Obliterated;
   p. pr. & vb. n. Obliterating.] [L. obliteratus, p. p. of
   obliterare to obliterate; ob (see Ob-) + litera, littera,
   letter. See Letter.]
   1. To erase or blot out; to efface; to render undecipherable,
      as a writing.
      [1913 Webster]

   2. To wear out; to remove or destroy utterly by any means; to
      render imperceptible; as, to obliterate ideas; to
      obliterate the monuments of antiquity.
      [1913 Webster]

            The harsh and bitter feelings of this or that
            experience are slowly obliterated.    --W. Black.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Obliterate \Ob*lit"er*ate\, a. (Zool.)
   Scarcely distinct; -- applied to the markings of insects.
   [1913 Webster]

WordNet (r) 3.0 (2006):

obliterate
    adj 1: reduced to nothingness [syn: blotted out, obliterate,
           obliterated]
    v 1: mark for deletion, rub off, or erase; "kill these lines in
         the President's speech" [syn: kill, obliterate, wipe
         out]
    2: make undecipherable or imperceptible by obscuring or
       concealing; "a hidden message"; "a veiled threat" [syn:
       obscure, blot out, obliterate, veil, hide]
    3: remove completely from recognition or memory; "efface the
       memory of the time in the camps" [syn: obliterate,
       efface]
    4: do away with completely, without leaving a trace

Moby Thesaurus II by Grady Ward, 1.0:

33 Moby Thesaurus words for "obliterate":
   absolve, annihilate, black out, blot, blot out, cancel,
   consign to oblivion, cross out, declare a moratorium, dele, delete,
   destroy, efface, eliminate, eradicate, erase, expunge, exterminate,
   extirpate, forgive, kill, nullify, raze, rub out, rule out,
   scratch, scratch out, sponge, sponge out, strike off, strike out,
   wipe out, write off