killer - definition and synonyms

noun [countable] 

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  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 US.

      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.