deadly

1 of 2

adjective

dead·​ly ˈded-lē How to pronounce deadly (audio)
deadlier; deadliest
1
: likely to cause or capable of producing death
deadly poison
2
a
: aiming to kill or destroy : implacable
a deadly enemy
b
: highly effective
a deadly exposé
c
: unerring
a deadly marksman
d
: marked by determination or extreme seriousness
3
a
: tending to deprive of force or vitality
a deadly habit
b
: suggestive of death especially in dullness or lack of animation
deadly bores
a deadly conversation
4
: very great : extreme
deadliness noun

deadly

2 of 2

adverb

1
archaic : in a manner to cause death : mortally
2
: suggesting death
3
: extremely
deadly serious
Choose the Right Synonym for deadly

deadly, mortal, fatal, lethal mean causing or capable of causing death.

deadly applies to an established or very likely cause of death.

a deadly disease

mortal implies that death has occurred or is inevitable.

a mortal wound

fatal stresses the inevitability of what has in fact resulted in death or destruction.

fatal consequences

lethal applies to something that is bound to cause death or exists for the destruction of life.

lethal gas

Examples of deadly in a Sentence

Adjective the world's most deadly snake a more deadly form of the disease They launched a deadly attack. Officers are allowed to use deadly force if necessary. She shoots with deadly accuracy. a basketball player with deadly aim A deadly silence followed his question. The two gang leaders are deadly enemies. He spoke with deadly seriousness. Adverb I'm deadly serious about making an offer on the house.
Recent Examples on the Web
Adjective
Rising nationalism under Modi has come alongside a similar phenomenon in China, where leader Xi Jinping has overseen an assertive foreign policy – though both sides have appeared to take steps to cool border tensions following the deadly 2020 clash. Simone McCarthy, CNN, 22 Mar. 2024 By this time last year, which was Kansas City’s deadliest year in its history, there were 38 homicides. Robert A. Cronkleton, Kansas City Star, 22 Mar. 2024 Even back in 2016 – when far fewer took the only land route between South and Central America than the half-million people who crossed in 2023 – it was overrun by deadly risks, from criminals to animals to racing rivers and pounding rain. Alfredo Sosa, The Christian Science Monitor, 22 Mar. 2024 Vaccination rates in the U.S. will likely be enough to prevent a repeat of the deadly waves of infections that claimed hundreds of lives and hospitalized thousands of children every year before the vaccine. Alexander Tin, CBS News, 22 Mar. 2024 The only problem: her initiation into the family includes a deadly game of hide-and-seek, where her culty in-laws chase her with guns and crossbows. Christian Allaire, Vogue, 22 Mar. 2024 Witnesses identified the suspect, 21, who was arrested on suspicion of assault with a deadly weapon. Kristina Davis, San Diego Union-Tribune, 22 Mar. 2024 Parler was originally removed from Apple and Google’s app stores after the deadly January 6 riot at the Capitol, due to the site’s inability or unwillingness to remove posts encouraging violence and crime. Makena Kelly, WIRED, 20 Mar. 2024 More:After deadly Clark County crash, what to know about the Amish communities in Wisconsin, Virginia James McCoy, around 45, was the driver of the van from Pounding Mill, Virginia. Drake Bentley, Journal Sentinel, 11 Mar. 2024
Adverb
About 10 minutes later, the spree turned deadly, police said. Antonio Planas, NBC News, 1 Feb. 2024 Pakistan launches deadly airstrikes in Iran Pakistan’s air force launched retaliatory airstrikes in Iran Thursday, killing at least nine people two days after Iran struck at separatist camps in Pakistan. Spencer Elliott, USA TODAY, 18 Jan. 2024 Some of the appointments — filmed on bare sets in clean, flat close-up, an aesthetic choice that stresses both their separation from reality and their plain emotional stakes — unfold in deadly earnest. Guy Lodge, Variety, 25 Jan. 2024 Texas wildfires turn deadly and keep growing Wildfires in the Texas Panhandle turned deadly, as officials in the city of Borger confirmed one death yesterday afternoon. Elizabeth Robinson, NBC News, 29 Feb. 2024 Measles is a highly contagious disease that can lead to complications and turn deadly, according to the CDC. Cnn.com Wire Service, The Mercury News, 26 Feb. 2024 The High Desert State Prison investigative services unit, the CDCR deadly force investigation team and the Lassen County District Attorney’s Office are investigating the incident. Ishani Desai, Sacramento Bee, 26 Jan. 2024 If new hardline measures are enacted, expect these Mexican cartels—some of the same ones that traffic deadly fentanyl into the U.S.—to turn eye-popping profits. TIME, 9 Jan. 2024 That, of course, led to the blind spot that helped make the Hamas attacks so deadly. Dahlia Scheindlin, Foreign Affairs, 29 Nov. 2023

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'deadly.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

First Known Use

Adjective

before the 12th century, in the meaning defined at sense 1

Adverb

before the 12th century, in the meaning defined at sense 1

Time Traveler
The first known use of deadly was before the 12th century

Dictionary Entries Near deadly

Cite this Entry

“Deadly.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/deadly. Accessed 29 Mar. 2024.

Kids Definition

deadly

1 of 2 adjective
dead·​ly ˈded-lē How to pronounce deadly (audio)
deadlier; deadliest
1
: likely to cause or capable of causing death
a deadly weapon
2
a
: aiming to kill or destroy
a deadly enemy
b
: very accurate : unerring
a deadly marksman
3
: very great : extreme
a deadly bore
deadliness noun

deadly

2 of 2 adverb
1
: suggesting death
deadly pale
2
: to a very great degree
deadly dull

Medical Definition

deadly

adjective
dead·​ly ˈded-lē How to pronounce deadly (audio)
deadlier; deadliest
: likely to cause or capable of causing death
a deadly disease
a deadly poison
a deadly instrument
deadliness noun

Legal Definition

deadly

adjective
dead·​ly
deadlier; deadliest
: likely to cause or capable of causing death
also : dangerous sense 2

Note: Deadly and dangerous are sometimes used interchangeably, especially in connection with weapons or instruments.

More from Merriam-Webster on deadly

Last Updated: - Updated example sentences
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