killer

American  

[kil-er] / ˈkɪl ər /

noun

• killers
  plural

1. a person or thing that kills.

2. killer whale.

3. a device used by a post office for printing cancellations on postage stamps.

4. a mark of cancellation made on a postage stamp.

5. Slang. something or someone having a formidable impact, devastating effect, etc..

   The math test was a real killer.

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adjective

Slang.

1. severe; powerful.

   a killer cold.

2. very difficult or demanding.

   a killer chess tournament.

3. highly effective; superior.

   a killer recipe for fried chicken.

killer British  

/ ˈkɪlə /

noun

1. 1. a person or animal that kills, esp habitually

   2. ( as modifier )

      a killer shark

2. something, esp a task or activity, that is particularly taxing or exhausting

3. an animal selected to be slaughtered for food

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Usage

What is a basic definition of killer? A killer is a person or thing that kills, meaning they end lives. Killer is also used in slang to mean something that is devastating or exhausting. Additionally, killer is used in slang to describe something as severe or powerful. Killer has several other meanings as a noun and an adjective. A person or thing that ends someone’s life is a killer. In terms of a person, killer is often used interchangeably with murderer. However, killer can refer to someone who killed another person by accident, while murderer is not used in that sense.

• Real-life examples: John Wilkes Booth was Abraham Lincoln’s killer. Jack the Ripper was an infamous killer. Bacteria and viruses often act as natural killers. People use weed killers on their lawns.
• Used in a sentence: My cat is a very effective killer of birds.

In slang, killer is used to describe something as causing stress, exhaustion, pain, or misery.

• Real-life examples: You might call a particularly hard test a killer test. A killer workout would push your body to the limits of its abilities.
• Used in a sentence: That history assignment turned out to be a killer and took me forever to finish.

In slang, killer is also used to describe something as severe, intense, or powerful.

• Real-world examples: You might call a baseball game that goes into extra innings with a 2–2 score, a killer game. If you come down with a severe cold that keeps you in bed for several days, you could call it a killer cold.
• Used in a sentence: After living abroad for five years, Michelle came down with a killer case of homesickness.

Other Word Forms

Derived Forms

• self-killer
  noun

Inflected Forms

Nouns

• killers
  plural

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Etymology

Origin of killer

First recorded in 1525–35; kill ¹ + -er ¹

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Example Sentences

See Examples For:

killer killers

Even the soaking tub and walk-in shower have killer views.

From MarketWatch ● Nov. 9, 2026

Natural killer cells avoid this complication because they are a different type of immune cell.

From Science Daily ● Nov. 8, 2026

Serial killer Steve Wright has been questioned about a series of cold cases but is "not currently a suspect" in any of them, the police have told the BBC.

From BBC ● Nov. 3, 2026

Come for my colleagues’ smart insights about the midterms, stay for their killer senses of humor.

From Slate ● Oct. 29, 2026

Someone tapped his shoulder, and, still on guard against zombies and killer dolls, he yelped.

From "Not Nothing" by Gayle Forman

Lubinets -- a lawyer by training and an ex-MP -- also faced criticism, with one Ukrainian soldier accusing him on Facebook of being "all too eager to smile and ingratiate himself with the killers".

From Barron's ● Nov. 3, 2026

Walking down Yablunska Street, Dulkay said thoughts of the victims drive him to pursue the killers and keep faith in eventual justice.

From The Wall Street Journal ● Oct. 26, 2026

But the crime remains unsolved – and in a new BBC documentary series Devine tells of his guilt over the way the attack unfolded, and for the failure to catch the killers.

From BBC ● Oct. 24, 2026

Representatives for the trust have argued Reiner is barred from accessing the fund due to California’s so-called Slayer Statute, which blocks convicted killers from profiting from their crimes in various ways, including through inheritance claims.

From Los Angeles Times ● Oct. 23, 2026

Unfortunately, a good many chemicals also have the power to separate oxidation from energy production, and the insecticides and weed killers are well represented on the list.

From "Silent Spring" by Rachel Carson

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