DEADLINESS 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

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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 blast last summer was the deadliest incident for the Sheriff’s Department in 150 years, triggering criminal investigations and more than $350,000 in fines from the California Division of Occupational Safety and Health. — Andrew Khouri, Los Angeles Times, 19 July 2026 The wreckage of a 49-foot cabin cruiser that capsized near Alcatraz Island this week has been located on the floor of San Francisco Bay, as authorities continue searching for two family members still missing after the deadly accident. — James Ward, USA Today, 18 July 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

The most common type is lethal in about half of patients, and death is almost instantaneous.

— Veronique Greenwood, Time, 13 July 2026
Tewalt previously cautioned state lawmakers that transitioning from lethal injection to a firing squad as Idaho’s preferred method would result in even more lawsuits.

— Kevin Fixler, Idaho Statesman, 10 July 2026

Definition of lethal

Adjective

The aspiring model was blooming in florals in the sculptural look, which featured a strapless bubble top paired with a sheer floor-length skirt, both of which were embroidered with purple and blue floral designs.

— Lara Walsh, InStyle, 18 July 2026
Yet, in the last two years, this sentiment of sheer doom has slowly and steadily begun to give way to a tentative yet very much present hope.

— Rafa Sales Ross, Variety, 18 July 2026

Definition of sheer

Adjective

Iran has been degraded by over 13,000 strikes, but has survived and reconstituted, rather than suffering a mortal blow.

— Nick Paton Walsh, CNN Money, 17 July 2026
The Greek myths are rife with petty and meddlesome deities squabbling, playing favorites, punishing harshly, and otherwise wreaking havoc on the lives of mortal men.

— Louis Peitzman, Vulture, 17 July 2026

Definition of mortal

Adverb

Be vigilant about never leaving young children and pets in vehicles without supervision, especially during periods of intense heat, as car interiors can quickly become extremely hot.

— CA Weather Bot, Sacbee.com, 14 July 2026
Surveillance of a suspect can take hours or days, and is extremely resource-intensive.

— Caroll Alvarado, CNN Money, 14 July 2026

Definition of extremely

Adjective

Like many Maine officials, Biddeford mayor Liam LaFountain has called for a thorough and transparent investigation into the fatal shooting of 26-year-old Joan Sebastian Guerrero at the hands of a federal agent.

— Caroll Alvarado, CNN Money, 14 July 2026
In the third season, Juliette has lost her memories in the process of surviving a near-fatal experience being locked in an incinerator.

— Dessi Gomez, Deadline, 13 July 2026

Definition of fatal

Adjective

Crocker, who survived the 1983 bombing of the US embassy in Beirut, Lebanon, said that at this point an unconditional opening of the Strait of Hormuz to all maritime traffic should be the objective.

— Monica Haider, CNN Money, 18 July 2026
Ramp, the corporate card and expense management company backed by Iconiq and valued at $44 billion, is now Senra’s largest advertiser and, by CEO Glyman’s own description, an unconditional backer.

— Lily Mae Lazarus, Fortune, 5 July 2026

Definition of unconditional

Adjective

The second a driving Kieran Tierney run that left Dani Carvajal for dead and again found McTominay crashing into the box.

— Jordan Campbell, New York Times, 18 July 2026
Life-threatening flash flooding has hit southern Texas after days of torrential rain, leaving at least two people dead and hundreds of people rescued across the same region struck by last July’s catastrophic floods.

— Dalia Faheid, CNN Money, 17 July 2026

Definition of dead

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“Deadly.” Merriam-Webster.com Thesaurus, Merriam-Webster, https://www.merriam-webster.com/thesaurus/deadly. Accessed 20 Jul. 2026.

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Synonyms of deadly

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