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
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
Michael Dorgan, FOXNews.com, 2 Jan. 2026
Crans-Montana, Switzerland — Investigators said Friday that the deadly fire that tore through a popular bar in the Swiss ski resort of Crans-Montana early on New Year's Day was caused by sparklers on Champagne bottles, which ignited the bar's ceiling.
—Ramy Inocencio, CBS News, 2 Jan. 2026
Mark Price, Charlotte Observer, 21 Dec. 2025
Fentanyl is a deadly synthetic opioid that’s pressed into counterfeit pills or mixed into heroin, cocaine and other street drugs.
—Lauren Penington, Denver Post, 4 Dec. 2025
See All Example Sentences for deadly
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Adjective
Swiss authorities on Friday began the grim task of identifying the mostly young victims of a deadly New Year’s Eve bar fire that killed around 40 people and injured 119 revelers at a ski resort in Crans-Montana.
—Michael Dorgan, FOXNews.com, 2 Jan. 2026
Crans-Montana, Switzerland — Investigators said Friday that the deadly fire that tore through a popular bar in the Swiss ski resort of Crans-Montana early on New Year's Day was caused by sparklers on Champagne bottles, which ignited the bar's ceiling.
—Ramy Inocencio, CBS News, 2 Jan. 2026
Adverb
Details of how the incident turned deadly later in the night have not been released.
—Mark Price, Charlotte Observer, 21 Dec. 2025
Fentanyl is a deadly synthetic opioid that’s pressed into counterfeit pills or mixed into heroin, cocaine and other street drugs.
—Lauren Penington, Denver Post, 4 Dec. 2025
See All Example Sentences for deadly
Cite this Entry
“Deadly.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/deadly. Accessed 4 Jan. 2026.
Copy CitationKids Definition
deadly
2 of 2 adverb1
: suggesting death
deadly pale
2
: to a very great degree
deadly dull
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