Did you know?

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

killer - 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.



Thesaurus diagram

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.

noun [countable]     killer pronunciation in American English
Word Forms
  1. 1
    someone who kills another person

    The young woman’s killer has not yet been found.

    a hired/trained killer

    a child/cop killer (=someone who has killed a child or police officer)

    1. a.
      something that kills people

      Cancer is the second largest killer in the U.S.

      a killer disease/virus

    2. b.
      something that kills or destroys something

      weed killer

      a passion killer

  2. 2
    informal something that is very difficult

    The test was a killer.

Open Dictionary


a rise in the level of a stream or river

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