The Collaborative International Dictionary of English v.0.48:

Ignorant \Ig"no*rant\, a. [F., fr. L. ignorans, -antis, p. pr.
   of ignorare to be ignorant. See Ignore.]
   1. Destitute of knowledge; uninstructed or uninformed;
      untaught; unenlightened.
      [1913 Webster]

            He that doth not know those things which are of use
            for him to know, is but an ignorant man, whatever he
            may know besides.                     --Tillotson.
      [1913 Webster]

   2. Unacquainted with; unconscious or unaware; -- used with
      of.
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            Ignorant of guilt, I fear not shame.  --Dryden.
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   3. Unknown; undiscovered. [Obs.]
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            Ignorant concealment.                 --Shak.
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            Alas, what ignorant sin have I committed? --Shak.
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   4. Resulting from ignorance; foolish; silly.
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            His shipping,
            Poor ignorant baubles! -- on our terrible seas,
            Like eggshells moved.                 --Shak.

   Syn: Uninstructed; untaught; unenlightened; uninformed;
        unlearned; unlettered; illiterate. -- Ignorant,
        Illiterate. Ignorant denotes lack of knowledge, either
        as to single subject or information in general;
        illiterate refers to an ignorance of letters, or of
        knowledge acquired by reading and study. In the Middle
        Ages, a great proportion of the higher classes were
        illiterate, and yet were far from being ignorant,
        especially in regard to war and other active pursuits.
        [1913 Webster]

              In such business
              Action is eloquence, and the eyes of the ignorant
              More learned than the ears.         --Shak.
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              In the first ages of Christianity, not only the
              learned and the wise, but the ignorant and
              illiterate, embraced torments and death.
                                                  --Tillotson.
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The Collaborative International Dictionary of English v.0.48:

Ignorant \Ig"no*rant\, n.
   A person untaught or uninformed; one unlettered or unskilled;
   an ignoramous.
   [1913 Webster]

         Did I for this take pains to teach
         Our zealous ignorants to preach?         --Denham.
   [1913 Webster]

WordNet (r) 3.0 (2006):

ignorant
    adj 1: uneducated in general; lacking knowledge or
           sophistication; "an ignorant man"; "nescient of
           contemporary literature"; "an unlearned group incapable
           of understanding complex issues"; "exhibiting contempt
           for his unlettered companions" [syn: ignorant,
           nescient, unlearned, unlettered]
    2: uneducated in the fundamentals of a given art or branch of
       learning; lacking knowledge of a specific field; "she is
       ignorant of quantum mechanics"; "he is musically illiterate"
       [syn: ignorant, illiterate]
    3: unaware because of a lack of relevant information or
       knowledge; "he was completely ignorant of the circumstances";
       "an unknowledgeable assistant"; "his rudeness was unwitting"
       [syn: ignorant, unknowledgeable, unknowing,
       unwitting]

Moby Thesaurus II by Grady Ward, 1.0:

122 Moby Thesaurus words for "ignorant":
   a novice at, a stranger to, awkward, benighted, blankminded,
   boorish, brainless, callow, crude, disaccustomed, discourteous,
   dumb, empty, empty-headed, foolish, fresh, gauche, green,
   green as grass, groping, gross, headless, ill-mannered, illiterate,
   immature, impolite, in the dark, inane, incognizant, inept,
   inexperienced, ingenuous, innocent, insensate, irrational,
   know-nothing, lackbrained, lean-minded, lean-witted, lowbrow,
   mindless, naive, nescient, new to, not bright, oblivious,
   of little brain, pea-brained, pin-brained, raw, reasonless, rude,
   rusty, senseless, simple, slackminded, slackwitted, strange to,
   tentative, unaccustomed, unaccustomed to, unacquainted,
   unacquainted with, unapprized, unaware, uncivil, uncomprehending,
   unconscious, unconversant, unconversant with, uncouth, uncultured,
   undeveloped, uneducated, unenlightened, unexperienced, unfamiliar,
   unfamiliar with, unfledged, ungifted, unhabituated, unhardened,
   unilluminated, uninformed, uninitiated, uninitiated in,
   uninstructed, unintellectual, unintelligent, uninured, unknowing,
   unlearned, unlettered, unmatured, unposted, unpracticed,
   unpracticed in, unprogressive, unread, unreasoning, unripe,
   unschooled, unseasoned, unskilled in, unsophisticated, unsure,
   untalented, untaught, unthinking, untrained, untried, untutored,
   unused, unused to, unversed, unversed in, unwise, unwitting,
   unwonted, vacuous, weaned, witless