DEADLY Synonyms: 324 Similar and Opposite Words

Q: How does the adjective 'deadly' differ from other similar words?

Some common synonyms of deadly are fatal , lethal , and mortal . While all these words mean "causing or capable of causing death," deadly applies to an established or very likely cause of death. // a deadly disease

Q: When would 'fatal' be a good substitute for 'deadly'?

In some situations, the words fatal and deadly are roughly equivalent. However, fatal stresses the inevitability of what has in fact resulted in death or destruction. // fatal consequences

Q: When is 'lethal' a more appropriate choice than 'deadly'?

While in some cases nearly identical to deadly , lethal applies to something that is bound to cause death or exists for the destruction of life. // lethal gas

Q: When could 'mortal' be used to replace 'deadly'?

The synonyms mortal and deadly are sometimes interchangeable, but mortal implies that death has occurred or is inevitable. // a mortal wound

deadly 1 of 2

adjective

ˈded-lē

Definition of deadly

as in lethal

likely to cause or capable of causing death the doctors were alarmed about the outbreak of the deadly new virus

Synonyms & Similar Words

Relevance

Antonyms & Near Antonyms

as in sheer

having no exceptions or restrictions the deadly tedium of waiting for the fog to lift

Synonyms & Similar Words

Antonyms & Near Antonyms

as in mortal

of, relating to, or suggestive of death a deadly pallor spread across her face as the tragic news gradually sank in

Synonyms & Similar Words

Antonyms & Near Antonyms

deadly

2 of 2

adverb

as in extremely

to a great degree I'm deadly serious about making an offer on the house

Synonyms & Similar Words

Antonyms & Near Antonyms

Synonym Chooser

How does the adjective deadly differ from other similar words?

Some common synonyms of deadly are fatal, lethal, and mortal. While all these words mean "causing or capable of causing death," deadly applies to an established or very likely cause of death.

a deadly disease

When would fatal be a good substitute for deadly?

In some situations, the words fatal and deadly are roughly equivalent. However, fatal stresses the inevitability of what has in fact resulted in death or destruction.

fatal consequences

When is lethal a more appropriate choice than deadly?

While in some cases nearly identical to deadly, lethal applies to something that is bound to cause death or exists for the destruction of life.

lethal gas

When could mortal be used to replace deadly?

The synonyms mortal and deadly are sometimes interchangeable, but mortal implies that death has occurred or is inevitable.

a mortal wound

Example Sentences

Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.

Recent Examples of deadly

Adjective

Instead of a larger and far deadlier outbreak, the outbreak ended with 11 cases in Chicago and one death. — Julie Morita, Time, 25 Oct. 2026 Meanwhile, deadly Russian attacks continue, as Ukraine raises concerns about cracks in support from the US. — Lauren Kent, CNN Money, 24 Oct. 2026

Adverb

MacDonald and editor Phil Hignett have a keen, witty sense of how the online realm crashes offline living, seamlessly integrating deadly-accurate TikTok parodies into the film’s breezy narrative flow. — Guy Lodge, Variety, 26 Aug. 2026 The disagreement leaves the government to determine when one of the world’s largest apparel-exporting industries must reopen a wage debate that turned deadly less than three years ago. — Alexandra Harrell, Footwear News, 24 Aug. 2026 See All Example Sentences for deadly

Recent Examples of Synonyms for deadly

Adjective

Garza was shot twice with less-lethal bean bag rounds but did not surrender.

— Richard Winton, Los Angeles Times, 24 Oct. 2026
Police said officers used a less-lethal weapon to subdue Sims and take him into custody.

— Rosalio Ahumada, Sacbee.com, 23 Oct. 2026

Definition of lethal

Adjective

The tracks, the engineers, the data, the media attention, the sheer amount of racing—the Formula 1 World Championship consists of twenty-plus races, on five continents, in nine months.

— Sam Knight, New Yorker, 22 Oct. 2026
The silhouette was mostly formfitting and streamlined, with emphasis at the hips and waist and a continuation of the contrasting sheer, black fabric running down the column skirt.

— Julia Teti, Footwear News, 22 Oct. 2026

Definition of sheer

Adjective

Airing for eight seasons between 1964 and 1972, the fantastical series followed the daily adventures of a powerful witch who attempted to live as a typical suburban housewife alongside her mortal husband.

— Justine Fisher, PEOPLE, 12 Oct. 2026
Waymo’s sales pitch is that its technology will remove all that mortal imperfection from our streets.

— Molly Fischer, New Yorker, 12 Oct. 2026

Definition of mortal

Adjective

Speed cameras have been shown to reduce speeding by 31% to 82% and fatal crashes by 53% to 71%, according to the Department of Transportation.

— Kevinisha Walker, Los Angeles Times, 26 Oct. 2026
Kumar faces two counts of first-degree manslaughter and three counts of recklessly endangering another person in Deschutes County stemming from the fatal wreck.

— Eric Mack , Bill Melugin, FOXNews.com, 26 Oct. 2026

Definition of fatal

Adjective

Here, the defining aspect of Benjamin Button’s strange existence is love — lucky, steady, unconditional.

— Sara Holdren, Vulture, 22 Oct. 2026
In 2024, Michigan State launched Rx Kids, the country’s first universal and unconditional prenatal and infant cash program.

— Mona Hanna, Washington Post, 8 Oct. 2026

Definition of unconditional

Adjective

Police said Sunday that a 65-year-old man was found dead on a sidewalk near an entrance to Disneyland in Anaheim.

— Alene Tchekmedyian, Los Angeles Times, 26 Oct. 2026
The vehicle arrived at a hospital, where Kohen was pronounced dead, and another individual was critically injured, according to authorities.

— Charlotte Phillipp, PEOPLE, 25 Oct. 2026

Definition of dead

Adverb

There's no doubt that Riley Green's acoustic performances are incredibly popular.

— David Hookstead OutKick, FOXNews.com, 26 Oct. 2026
These teachers work with students who have an incredibly diverse set of needs, including those with autism, learning disabilities such as dyslexia, developmental delays and physical disabilities.

— Jonaki Mehta, NPR, 26 Oct. 2026

Definition of incredibly

Cite this Entry

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“Deadly.” Merriam-Webster.com Thesaurus, Merriam-Webster, https://www.merriam-webster.com/thesaurus/deadly. Accessed 28 Oct. 2026.

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Synonyms of deadly

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adverb

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