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

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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

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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

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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

The latest attempt comes two weeks after tens of thousands of would-be migrants, driven by poverty and misinformation, rushed toward Ceuta in one of the deadliest migration crises to hit the region. — ABC News, 16 Aug. 2026 In 2010, both Canada and the United States began allowing Haitians to live in their countries following a deadly earthquake and subsequent political upheaval in their country. — Trevor Hughes, USA Today, 15 Aug. 2026

Adverb

Like those albums, LP4 operates with its own sense of logic and time, sounding alternately playful and deadly serious, proudly complex and refreshingly pared back. — Sam Sodomsky, Pitchfork, 4 May 2026 In Langbein’s comic, but also deadly serious, imagination, this is no mere metaphor. — Los Angeles Times, 22 Apr. 2026 See All Example Sentences for deadly

Recent Examples of Synonyms for deadly

Adjective

Nothing is perfect, as the conductor of potentially lethal vehicles that, in some ways, defy physics.

— John Werner, Forbes.com, 10 Aug. 2026
The church has no difficulty prescribing specifics when the subject is autonomous lethal weapons.

— Foreign Affairs, Foreign Affairs, 10 Aug. 2026

Definition of lethal

Adjective

Other governments, including the US, have their own rules and disclosure requirements, but beyond the breadth of the controls in China, the sheer number of people affected is striking – and reaches far beyond civil servants.

— Sylvie Zhuang, CNN Money, 16 Aug. 2026
Just look at the new stand — the sheer size of it shows the club’s ambition.

— Richard Sutcliffe, New York Times, 16 Aug. 2026

Definition of sheer

Adjective

By suggesting that Black women would willingly place their own children in mortal danger for profit, such narratives provided yet another means of humiliating, degrading and dehumanizing African Americans.

— The Conversation, The Conversation, 11 Aug. 2026
What would be the worst moment in a mere mortal’s career, Hoecht turned into a valiant scene.

— Tim Graham, New York Times, 4 Aug. 2026

Definition of mortal

Adjective

The bureau, which faces little public accountability in fatal shootings, declined to comment for this story.

— Isabelle Chapman, CNN Money, 10 Aug. 2026
The man who prosecutors say orchestrated the 1996 killing of rap icon Tupac Shakur is scheduled to go to trial Monday, almost 30 years after the fatal drive-by shooting in Las Vegas.

— CBS News, CBS News, 10 Aug. 2026

Definition of fatal

Adjective

Hinckley launched a music career after being granted unconditional release in 2022, but found some concert venues weren’t receptive to hosting his performances.

— Brian Niemietz, New York Daily News, 12 Aug. 2026
In one room, Catherine is getting promises of unconditional love and affection from Alden, a man who would never harm her.

— Erin Qualey, Vulture, 10 Aug. 2026

Definition of unconditional

Adjective

This one stars Cox himself as a mysterious and formidable old man in an undertaker’s suit and parson’s hat who wanders into an Arizona border town in 1890 to gather the names of dead Mexican laborers.

— Owen Gleiberman, Variety, 15 Aug. 2026
His mother, Sudha Venkatesan, 45, and his brother, Siddharth Aravind, 14, were found dead Tuesday in their home in Acton, some 20 miles northwest of Boston, prosecutors said.

— Rebekah Riess, CNN Money, 15 Aug. 2026

Definition of dead

Cite this Entry

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“Deadly.” Merriam-Webster.com Thesaurus, Merriam-Webster, https://www.merriam-webster.com/thesaurus/deadly. Accessed 17 Aug. 2026.

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Synonyms of deadly

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adverb

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