deadly
Americanadjective
-
deadlier,
comparative
-
deadliest
superlative
-
causing or tending to cause death; fatal; lethal.
a deadly poison.
-
aiming to kill or destroy; implacable.
a deadly enemy.
-
like death.
a deadly pallor.
-
excruciatingly boring.
The dinner party was absolutely deadly.
-
deadly haste.
-
extremely accurate.
Annie Oakley was a deadly shot.
adverb
-
in a manner resembling or suggesting death.
deadly pale.
-
excessively; completely.
deadly dull.
adjective
-
likely to cause death
deadly poison
deadly combat
-
informal extremely boring
adverb
Synonym Usage
See fatal.
Other Word Forms
Derived Forms
Inflected Forms
Adjectives
Etymology
Origin of deadly
First recorded before 900; Middle English deedli(ch), Old English dēadlīce; see dead, -ly
Explanation
Something that's deadly can kill you. Because a gun can end someone's life, it's a deadly weapon. If someone's diagnosed with a deadly disease, it's lethal — it's capable of ending the person's life. When you hear someone talk about police officers using "deadly force," they mean actions that intended to cause death, or understood to be capable of killing someone. You can also use the word to mean "extremely" or "very," as when you describe your math class as deadly boring.
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
See Examples For:
And that’s the genius, in a way, of Elon Musk: he’s constantly saying stuff that is deadly serious and a joke at the same time.
From Salon ● Oct. 16, 2026
And in a setting where a mistranslated word can mean the difference between an accurate diagnosis and a dangerous mistake, the consequences can be severe—or even deadly.
From Slate ● Oct. 16, 2026
Saudi airlines are racing to evacuate up to $4 billion worth of aircraft from Riyadh Airport following deadly Houthi missile strikes.
From The Wall Street Journal ● Oct. 14, 2026
A 6ft 2in English striker with a deadly finishing touch, who came through at Spurs before learning his trade in the Football League.
From BBC ● Oct. 12, 2026
The light glinted off his spectacles; beneath the dark, glossy hair his face was deadly pale.
From "The Secret History" by Donna Tartt
"Weapons evolve faster than political decisions meant to stop them," Zelensky said, saying that the Iranian-designed Shahed drones that Russia uses have become much deadlier as the war drags on.
From Barron's ● Feb. 14, 2026
Through these mutations, they can become more contagious, evade immunity, and become deadlier.
From Salon ● Nov. 28, 2025
While about 500,000 people a year die from excessive heat, he says, “surprisingly, excessive cold is far deadlier, killing nearly ten times more.”
From The Wall Street Journal ● Oct. 30, 2025
Only dioxins, which come primarily from burning waste materials, are deadlier than airborne hexavalent chromium.
From Los Angeles Times ● Oct. 13, 2025
For one reason or another, the virus became a lot deadlier.
From "The Tipping Point" by Malcolm Gladwell
One of the deadliest saboteurs in recent military history, Lt.
From The Wall Street Journal ● Oct. 16, 2026
The 21-mile stretch of Pacific Coast Highway that runs through Malibu is one of the state’s deadliest and most notorious roads, with an average of about four crash-related fatalities per year over the last decade.
From Los Angeles Times ● Oct. 4, 2026
Global Witness says that 85% of the documented killings took place in Latin America, making it the deadliest region for every year since the group started publishing its reports in 2012.
From BBC ● Sep. 16, 2026
The 27-year-old from Moscow, who switched allegiance to Kazakhstan in 2018 in search of greater support, is the deadliest server on the women’s circuit.
From The Wall Street Journal ● Sep. 12, 2026
That they would all soon find themselves caught in the middle of one of the deadliest disease outbreaks in history.
From "I Survived the Great Molasses Flood, 1919" by Lauren Tarshis
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