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

Gomez twists the knife deeper for a good cause: He wants you not just to look but to really see.

From Los Angeles Times • Apr. 17, 2026

He died of heart failure and acute pulmonary edema -- a condition where fluid accumulates in the lungs -- two weeks after going under the knife.

From Barron's • Apr. 14, 2026

A £1.2m investment is planned to provide specialist training in schools most affected by knife crime, fund measures such as mentoring for high-risk students, and the deployment of chaperones on school routes.

From BBC • Apr. 6, 2026

It comes as the government is due to launch its crackdown on knife crime.

From BBC • Apr. 6, 2026

At least, thought Torak, he has his weapons with him, and my knife for company.

From "Wolf Brother" by Michelle Paver

Related Words

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