Did you know?

Click any word in a definition or example to find the entry for that word

ill - definition and synonyms


What are red words?

90% of the time, speakers of English use just 7,500 words in speech and writing. These words appear in red, and are graded with stars. One-star words are frequent, two-star words are more frequent, and three-star words are the most frequent.



The thesaurus of synonyms and related words is fully integrated into the dictionary. Click on the thesaurus category heading under the button in an entry to see the synonyms and related words for that meaning.

adjective ill pronunciation in British English /ɪl/
Word Forms
  • Facebook
  • Twitter
  1. 1
    not healthy, because of a medical condition or an injury. The usual American word is sick
    He’s been ill for a couple of weeks.
    She was too ill to travel.
    mentally ill patients
    terminally ill (=going to die because of an illness)
    seriously/critically ill: Her husband is seriously ill in hospital.
    fall ill /be taken ill (=become ill): She was unlucky enough to fall ill on holiday.
    ill with: Samantha was seriously ill with a fever.
  2. 2
    [only before noun] bad, or harmful
    Their defeat was mainly due to their ill-discipline.
    The fish didn’t taste fresh, but we suffered no ill effects.
    ill temper/humour: Bouts of ill temper punctuated the match.


a course of study which is much shorter than a university course and focuses on the skills you need for a job, especially computer-related skills

BuzzWord Article

Open Dictionary


an ancient Roman system of underfloor heating, used to heat houses with hot air; from the Latin 'hypocaustum'

add a word


A must for anyone with an interest in the changing face of language. The Macmillan Dictionary blog explores English as it is spoken around the world today.

global English and language change from our blog