Definition of ill adjective from the Oxford Advanced American Dictionary

      

    ill

     adjective
    adjective
    NAmE//ɪl//
     
     
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  1. 1 [not usually before noun] suffering from an illness or disease; not feeling well synonym sick Her father is seriously ill in St. Luke's hospital. She was taken ill suddenly. We both started to feel ill shortly after the meal. Uncle Harry is terminally ill with cancer (= he will die from his illness). the mentally ill (= people with a mental illness) (formal) He fell ill and died soon after.
  2. 2[usually before noun] bad or harmful He resigned because of ill health (= he was often ill). She suffered no ill effects from the experience. a woman of ill repute (= considered to be immoral)
  3. 3(formal) that brings, or is thought to bring, bad luck a bird of ill omen
  4. Idioms
    bad/ill feeling(also bad/ill feelings)
     
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    anger between people, especially after an argument or a disagreement There was a lot of bad feeling between the two groups of students.
    ill at ease
     
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    feeling uncomfortable and embarrassed Ifelt ill at ease in such formal clothes.
    it's an ill wind (that blows nobody any good)(saying)
     
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    no problem is so bad that it does not bring some advantage to someone
See the Oxford Advanced Learner's Dictionary entry: ill