The Collaborative International Dictionary of English v.0.48:

Ignore \Ig*nore"\, v. t. [imp. & p. p. Ignored; p. pr. & vb.
   n. Ignoring.] [L. ignorare; pref. in- not + the root of
   gnarus knowing, noscere to become acquainted with. See
   Know, and cf. Narrate.]
   1. To be ignorant of or not acquainted with. [Archaic]
      [1913 Webster]

            Philosophy would solidly be established, if men
            would more carefully distinguish those things that
            they know from those that they ignore. --Boyle.
      [1913 Webster]

   2. (Law) To throw out or reject as false or ungrounded; --
      said of a bill rejected by a grand jury for lack of
      evidence. See Ignoramus.
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   3. Hence: To refuse to take notice of; to shut the eyes to;
      not to recognize; to disregard willfully and causelessly;
      as, to ignore certain facts; to ignore the presence of an
      objectionable person.
      [1913 Webster]

            Ignoring Italy under our feet,
            And seeing things before, behind.     --Mrs.
                                                  Browning.
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WordNet (r) 3.0 (2006):

ignore
    v 1: refuse to acknowledge; "She cut him dead at the meeting"
         [syn: ignore, disregard, snub, cut]
    2: bar from attention or consideration; "She dismissed his
       advances" [syn: dismiss, disregard, brush aside, brush
       off, discount, push aside, ignore]
    3: fail to notice [ant: mark, note, notice]
    4: give little or no attention to; "Disregard the errors" [syn:
       neglect, ignore, disregard]
    5: be ignorant of or in the dark about [ant: cognise,
       cognize, know]