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 American English /ɪl/
Word Forms
  • Facebook
  • Twitter
  1. 1
    not healthy, because of a medical condition or an injury

    He’s been ill for a couple of weeks.

    She was too ill to travel.

    terminally ill (=going to die because of an illness)

    seriously/critically ill:

    Her husband is seriously ill in the hospital.

    fall ill /be taken ill (=become ill):

    She was unlucky enough to fall ill on vacation.

    ill with:

    Sarah was seriously ill with a fever.

    See also sick1
  2. 2
    [only before noun] formal 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/humor:

    Bouts of ill temper punctuated the match.



to fall over forwards so that your face hits the ground or another surface

BuzzWord Article

Open Dictionary


the activity of exploring abandoned buildings and other manmade structures

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
Macmillan learn live love play