le·​thal | \ ˈlē-thəl How to pronounce lethal (audio) \

Definition of lethal

 (Entry 1 of 2)

1a : of, relating to, or causing death death by lethal injection
b : capable of causing death lethal chemicals
2 : gravely damaging or destructive : devastating a lethal attack on his reputation
3 : very potent or effective a lethal fastball also : having a high alcohol content a lethal rum punch



Definition of lethal (Entry 2 of 2)

1 : an abnormality of genetic origin causing the death of the organism possessing it

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Other Words from lethal


lethality \ lē-​ˈtha-​lə-​tē How to pronounce lethality (audio) \ noun
lethally \ ˈlē-​thə-​lē How to pronounce lethally (audio) \ adverb

Synonyms & Antonyms for lethal

Synonyms: Adjective

Antonyms: Adjective

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Choose the Right Synonym for lethal


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 lethal in a Sentence

Adjective a potentially lethal dose of a drug He was sentenced to death by lethal injection.
Recent Examples on the Web: Adjective Human hunters can use extremely efficient lethal technologies. Jason G. Goldman, Scientific American, "How the Coronavirus Has Changed Animals’ Landscape of Fear," 21 May 2020 Instead, groups have expanded their territories, and confrontations have led to an increasingly lethal landscape. Whitney Eulich, The Christian Science Monitor, "A helping hand? Amid pandemic, gangs cast themselves as protectors.," 19 May 2020 Medical workers said later that Mr. Loescher survived because he had been pinned upside down, preventing a lethal loss of blood. Emmett Lindner, BostonGlobe.com, "Gil Loescher, refugees expert who survived Iraq bombing, dies at 75," 17 May 2020 Anaya’s gorgeous ex-BFF Petra doesn’t have zit issues, but her allergy is a rare and lethal one: water. Daniel Kraus, New York Times, "A Few Brave Kids Battle a Toxic World," 16 May 2020 Yet, even more broadly, these are remarkably blunt tools against a lethal, contagious disease. Washington Post, "The limits of smartphone data are on display as the country seeks to reopen," 14 May 2020 Others are taking a unique approach to avoid the lethal measures of last resort. Michael Casagrande | Mcasagrande@al.com, al, "Why millions of pigs are being euthanized," 14 May 2020 The situation grew desperate in winter, when night temperatures plunged to lethal lows. Robert Clark, National Geographic, "‘I have had, in my life, whole squadrons of guardian angels looking after me. There’s no other way.’," 6 May 2020 In one particularly lethal spate in 2013, 42 Chinese people died and more than 1,600 were injured from the hornets’ stings. Alexandra Ossola, Quartz, "The “murder hornet” is as bad as it sounds," 3 May 2020

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'lethal.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of lethal


circa 1604, in the meaning defined at sense 1a


1917, in the meaning defined at sense 1

History and Etymology for lethal

Adjective and Noun

Latin letalis, lethalis, from letum death

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Time Traveler for lethal

Time Traveler

The first known use of lethal was circa 1604

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Statistics for lethal

Last Updated

29 May 2020

Cite this Entry

“Lethal.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/lethal. Accessed 4 Jun. 2020.

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More Definitions for lethal


How to pronounce lethal (audio)

English Language Learners Definition of lethal

: causing or able to cause death


le·​thal | \ ˈlē-thəl How to pronounce lethal (audio) \

Medical Definition of lethal

 (Entry 1 of 2)

: of, relating to, or causing death a lethal injury also : capable of causing death lethal chemicals a lethal dose

Other Words from lethal

lethality \ lē-​ˈthal-​ət-​ē How to pronounce lethality (audio) \ noun, plural lethalities
lethally adverb



Medical Definition of lethal (Entry 2 of 2)

1 : an abnormality of genetic origin causing the death of the organism possessing it usually before maturity

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More from Merriam-Webster on lethal

Thesaurus: All synonyms and antonyms for lethal

Spanish Central: Translation of lethal

Nglish: Translation of lethal for Spanish Speakers

Britannica English: Translation of lethal for Arabic Speakers

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