knife

American  

[nahyf] / naɪf /

noun

plural

knives

1. an instrument for cutting, consisting essentially of a thin, sharp-edged, metal blade fitted with a handle.

2. a knifelike weapon; dagger or short sword.

3. any blade for cutting, as in a tool or machine.

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verb (used with object)

knifed, knifing

1. to apply a knife to; cut, stab, etc., with a knife.

2. to attempt to defeat or undermine in a secret or underhanded way.

verb (used without object)

knifed, knifing

1. to move or cleave through something with or as if with a knife.

   The ship knifed through the heavy seas.

idioms

1. under the knife, in surgery; undergoing a medical operation.

   The patient was under the knife for four hours.

knife British  

/ naɪf /

noun

1. a cutting instrument consisting of a sharp-edged often pointed blade of metal fitted into a handle or onto a machine

2. a similar instrument used as a weapon

3. to have a grudge against or victimize someone

4. to make a bad situation worse in a deliberately malicious way

5. people are determined to harm or put a stop to someone

   the knives are out for Stevens

6. undergoing a surgical operation

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verb

1. to cut, stab, or kill with a knife

2. to betray, injure, or depose in an underhand way

knife More Idioms  

1. see at gunpoint (knifepoint); under the knife; you could cut it with a knife.

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Other Word Forms

• knifelike
  adjective
• knifer
  noun

Etymology

Origin of knife

before 1100; Middle English knif, Old English cnīf; cognate with Dutch knijf, German Kneif, Old Norse knīfr

Explanation

A knife is a sharp tool that's used for slicing or cutting. We suggest using a knife as a kitchen tool instead of as a weapon. A bread knife has a long, serrated edge, and the blade of a pocket knife folds into its handle so you can safely carry it in your pocket. Surgeons use very small knives to make delicate cuts during operations, and various kinds of knives are sometimes used as weapons. To knife, in fact, is to stab or cut with a knife, almost always in a violent way.

Example Sentences

“Kevin is extraordinary. He’s been like a Swiss army knife at Duquesne. He runs our private equity, he helps with economic forecasts. He handles the networking outside the firm.”

From MarketWatch • May 7, 2026

A man who intervened during a knife attack on a Jewish man in Golders Green has told the BBC how he was trying to save a life.

From BBC • May 3, 2026

“Both officers expressed their fear of the imminent threat that they believe this victim posed to them, based on the knife and his prior actions.”

From Los Angeles Times • May 2, 2026

But Standard Oil finally went under the knife in 1911, split into 34 separate companies that sometimes seem like they are bent on reunifying.

From Barron's • May 2, 2026

He took out his knife and carved an SOS message in English into the shell of the coconut.

From "Fallout: Spies, Superbombs, and the Ultimate Cold War Showdown" by Steve Sheinkin

Related Words

• bayonet
• blade
• cutter
• dagger
• machete
• scalpel
• sickle
• skewer
• sword