The Collaborative International Dictionary of English v.0.48:

Ill \Ill\ ([i^]l), a. [The regular comparative and superlative
   are wanting, their places being supplied by worseand worst,
   from another root.] [OE. ill, ille, Icel. illr; akin to Sw.
   illa, adv., Dan. ilde, adv.]
   1. Contrary to good, in a physical sense; contrary or opposed
      to advantage, happiness, etc.; bad; evil; unfortunate;
      disagreeable; unfavorable.
      [1913 Webster]

            Neither is it ill air only that maketh an ill seat,
            but ill ways, ill markets, and ill neighbors.
                                                  --Bacon.
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            There 's some ill planet reigns.      --Shak.
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   2. Contrary to good, in a moral sense; evil; wicked; wrong;
      iniquitious; naughtly; bad; improper.
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            Of his own body he was ill, and gave
            The clergy ill example.               --Shak.
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   3. Sick; indisposed; unwell; diseased; disordered; as, ill of
      a fever.
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            I am in health, I breathe, and see thee ill. --Shak.
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   4. Not according with rule, fitness, or propriety; incorrect;
      rude; unpolished; inelegant.
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            That 's an ill phrase.                --Shak.
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   Ill at ease, uneasy; uncomfortable; anxious. "I am very ill
      at ease." --Shak.

   Ill blood, enmity; resentment; bad blood.

   Ill breeding, lack of good breeding; rudeness.

   Ill fame, ill or bad repute; as, a house of ill fame, a
      house where lewd persons meet for illicit intercourse.

   Ill humor, a disagreeable mood; bad temper.

   Ill nature, bad disposition or temperament; sullenness;
      esp., a disposition to cause unhappiness to others.

   Ill temper, anger; moroseness; crossness.

   Ill turn.
      (a) An unkind act.
      (b) A slight attack of illness. [Colloq. U.S.] -- Ill
   will, unkindness; enmity; malevolence.

   Syn: Bad; evil; wrong; wicked; sick; unwell.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Ill \Ill\, n.
   1. Whatever annoys or impairs happiness, or prevents success;
      evil of any kind; misfortune; calamity; disease; pain; as,
      the ills of humanity.
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            Who can all sense of others' ills escape
            Is but a brute at best in human shape. --Tate.
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            That makes us rather bear those ills we have
            Than fly to others that we know not of. --Shak.
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   2. Whatever is contrary to good, in a moral sense;
      wickedness; depravity; iniquity; wrong; evil.
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            Strong virtue, like strong nature, struggles still,
            Exerts itself, and then throws off the ill.
                                                  --Dryden.
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The Collaborative International Dictionary of English v.0.48:

Ill \Ill\, adv.
   In a ill manner; badly; weakly.
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         How ill this taper burns!                --Shak.
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         Ill fares the land, to hastening ills a prey,
         Where wealth accumulates and men decay.  --Goldsmith.
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   Note: Ill, like above, well, and so, is used before many
         participal adjectives, in its usual adverbal sense.
         When the two words are used as an epithet preceding the
         noun qualified they are commonly hyphened; in other
         cases they are written separatively; as, an
         ill-educated man; he was ill educated; an ill-formed
         plan; the plan, however ill formed, was acceptable. Ao,
         also, the following: ill-affected or ill affected,
         ill-arranged or ill arranged, ill-assorted or ill
         assorted, ill-boding or ill boding, ill-bred or ill
         bred, ill-conditioned, ill-conducted, ill-considered,
         ill-devised, ill-disposed, ill-doing, ill-fairing,
         ill-fated, ill-favored, ill-featured, ill-formed,
         ill-gotten, ill-imagined, ill-judged, ill-looking,
         ill-mannered, ill-matched, ill-meaning, ill-minded,
         ill-natured, ill-omened, ill-proportioned,
         ill-provided, ill-required, ill-sorted, ill-starred,
         ill-tempered, ill-timed, ill-trained, ill-used, and the
         like.
         [1913 Webster]

WordNet (r) 3.0 (2006):

ill
    adv 1: (`ill' is often used as a combining form) in a poor or
           improper or unsatisfactory manner; not well; "he was ill
           prepared"; "it ill befits a man to betray old friends";
           "the car runs badly"; "he performed badly on the exam";
           "the team played poorly"; "ill-fitting clothes"; "an ill-
           conceived plan" [syn: ill, badly, poorly] [ant:
           good, well]
    2: unfavorably or with disapproval; "tried not to speak ill of
       the dead"; "thought badly of him for his lack of concern"
       [syn: ill, badly] [ant: well]
    3: with difficulty or inconvenience; scarcely or hardly; "we can
       ill afford to buy a new car just now"
    adj 1: affected by an impairment of normal physical or mental
           function; "ill from the monotony of his suffering" [syn:
           ill, sick] [ant: well]
    2: resulting in suffering or adversity; "ill effects"; "it's an
       ill wind that blows no good"
    3: distressing; "ill manners"; "of ill repute"
    4: indicating hostility or enmity; "you certainly did me an ill
       turn"; "ill feelings"; "ill will"
    5: presaging ill fortune; "ill omens"; "ill predictions"; "my
       words with inauspicious thunderings shook heaven"-
       P.B.Shelley; "a dead and ominous silence prevailed"; "a by-
       election at a time highly unpropitious for the Government"
       [syn: ill, inauspicious, ominous]
    n 1: an often persistent bodily disorder or disease; a cause for
         complaining [syn: ailment, complaint, ill]

Moby Thesaurus II by Grady Ward, 1.0:

167 Moby Thesaurus words for "ill":
   abomination, affection, ailing, ailment, amiss, apocalyptic,
   atrocity, bad, badly, baleful, bane, baneful, befoulment,
   below par, black, blight, bodeful, boding, complaint, condition,
   corruption, criminal, critically ill, crying evil, damage,
   damaging, dark, defilement, deleterious, despoliation, destruction,
   detriment, detrimental, dire, disadvantageously, disagreeable,
   disagreeably, discourteous, disease, disorder, disrespectful,
   doomful, down, dreary, evil, evil-starred, evilly, faint, faintish,
   fateful, feeling awful, feeling faint, feeling something terrible,
   foreboding, gloomy, grievance, harm, havoc, hurt, hurtful,
   ill-boding, ill-bred, ill-fated, ill-mannered, ill-omened,
   ill-starred, impertinent, impolite, improper, in danger,
   inaccurate, inauspicious, incline, inconveniently, indisposed,
   inexpedient, infection, inferior, infirmity, inhospitable,
   inhospitably, inimical, injurious, injury, invalid, laid low,
   lowering, malady, malevolent, menacing, mischief, mortally ill,
   not quite right, of evil portent, off-color, ominous, out of sorts,
   outrage, peccant, poison, pollution, portending, portentous, rocky,
   rude, seedy, sick, sick unto death, sickish, sickness, sinful,
   sinister, somber, syndrome, taken ill, the worst, threatening,
   toxin, unadvantageously, unaffectionate, unaffectionately,
   unamiable, unamiably, unbenign, unbenignant, unbenignantly,
   unbenignly, uncompassionate, uncompassionately, uncompassioned,
   uncordial, uncordially, under the weather, unfavorable,
   unfortunate, unfriendly, ungenial, ungenially, ungracious,
   ungraciously, unhandily, unhealthy, unkind, unkindly, unloving,
   unlovingly, unlucky, unpleasant, unprofitably, unpromising,
   unpropitious, unrewardingly, unskillful, unsympathetic,
   unsympathetically, unsympathizing, untoward, unwell, uselessly,
   venom, vexation, vicious, wicked, with difficulty, woe, wrong,
   wrongly