deadly
Americanadjective
-
causing or tending to cause death; fatal; lethal.
a deadly poison.
-
aiming to kill or destroy; implacable.
a deadly enemy.
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like death.
a deadly pallor.
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excruciatingly boring.
The dinner party was absolutely deadly.
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deadly haste.
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extremely accurate.
Annie Oakley was a deadly shot.
adverb
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in a manner resembling or suggesting death.
deadly pale.
-
excessively; completely.
deadly dull.
adjective
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likely to cause death
deadly poison
deadly combat
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informal extremely boring
adverb
Related Words
See fatal.
Other Word Forms
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.
In the early 2000s, deadly accidents were common in China's coal mining industry.
From BBC • May 23, 2026
Tens of thousands of demonstrators massed in central Belgrade Saturday to renew calls for early elections that grew out of the anti-corruption movement sparked by a deadly rail station disaster.
From Barron's • May 23, 2026
The risk from the deadly Ebola outbreak has been raised to the highest level for the Democratic Republic of Congo, the World Health Organization said Friday, as the toll continued to rise.
From Barron's • May 22, 2026
Ebola is very deadly, but unlikely to cause a pandemic because it doesn’t spread easily.
From The Wall Street Journal • May 22, 2026
Mother let her look through the microscope at wiggling creatures that lived inside the tsetse flies and made them deadly.
From "A Girl Named Disaster" by Nancy Farmer
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
