Source : Webster's Revised Unabridged Dictionary (1913)

Ill \Ill\, 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.

            Neither is it ill air only that maketh an ill seat,
            but ill ways, ill markets, and ill neighbors.
                                                  --Bacon.

            There 's some ill planet reigns.      --Shak.

   2. Contrary to good, in a moral sense; evil; wicked; wrong;
      iniquitious; naughtly; bad; improper.

            Of his own body he was ill, and gave The clergy ill
            example.                              --Shak.

   3. Sick; indisposed; unwell; diseased; disordered; as, ill of
      a fever.

            I am in health, I breathe, and see thee ill. --Shak.

   4. Not according with rule, fitness, or propriety; incorrect;
      rude; unpolished; inelegant.

            That 's an ill phrase.                --Shak.

   {Ill at ease}, uneasy; uncomfortable; anxious. ``I am very
      ill at ease.'' --Shak.

   {Ill blood}, enmity; resentment.

   {Ill breeding}, want 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.

Source : WordNet®

ill humor
     n : an angry and disagreeable mood [syn: {ill humour}, {distemper}]
         [ant: {good humor}]