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

Keep scrolling for more

Other Words from lethal


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

Synonyms & Antonyms for lethal

Synonyms: Adjective

Antonyms: Adjective

Visit the Thesaurus for More 

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 Community members have pushed back against that notion, saying even displaying a less-lethal weapon like beanbag shotguns or Tasers could escalate a situation. David Hernandez, San Diego Union-Tribune, 17 Oct. 2021 Zach Charbonnet, so lethal against LSU, gained just 19 yards — and force Thompson-Robinson to beat them. Bill Plaschke, Los Angeles Times, 19 Sep. 2021 Autonomous weapons are already a clear and present danger, and will become more intelligent, nimble, lethal, and accessible at an alarming speed. Kai-fu Lee, The Atlantic, 11 Sep. 2021 These crimes have profoundly damaging, and sometimes lethal consequences for service members and our families, and fundamentally impact our combat readiness. CBS News, 8 Sep. 2021 For thousands of police officers in Washington state, taser guns are now the only less-lethal weapon available to them. Dan Springer, Fox News, 7 Sep. 2021 That increase is largely due to the rise of fentanyl, a synthetic opioid that is exponentially more powerful — and lethal — than heroin. Yoohyun Jung, San Francisco Chronicle, 30 June 2021 Getting it right means fielding successors to the retired Kiowa scout helicopter and ubiquitous Black Hawk assault helicopter that are much more lethal, survivable, and affordable. Loren Thompson, Forbes, 11 June 2021 Lang, who is now 77, also took care of her husband when he was diagnosed with a fast-moving, and ultimately lethal, type of prostate cancer. Daniela Altimari, courant.com, 30 May 2021 Recent Examples on the Web: Noun Almost 8 of 10 lethal overdose victims had no contact with the agency before their deaths, the report found. Washington Post, 4 Sep. 2020 In response to Russian operations and Chinese advances, the USAF is battling for air superiority in the Arctic with its most valuable—and lethal—assets in Alaska, including the F-22A Raptor and F-35A Joint Strike Fighter. Jeff Bolton, Popular Mechanics, 19 July 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.

See More

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

Keep scrolling for more

Learn More About lethal

Time Traveler for lethal

Time Traveler

The first known use of lethal was circa 1604

See more words from the same year

Dictionary Entries Near lethal

let go of


lethal gene

See More Nearby Entries 

Statistics for lethal

Last Updated

23 Oct 2021

Cite this Entry

“Lethal.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/lethal. Accessed 27 Oct. 2021.

Style: MLA
MLACheck Mark Icon ChicagoCheck Mark Icon APACheck Mark Icon Merriam-WebsterCheck Mark Icon

Keep scrolling for more

More Definitions for lethal



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 lethal (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

More from Merriam-Webster on lethal

Nglish: Translation of lethal for Spanish Speakers

Britannica English: Translation of lethal for Arabic Speakers


Test Your Vocabulary

Farm Idioms Quiz

  • cow coming home
  • What does 'poke' refer to in the expression 'pig in a poke'?
Spell It

Can you spell these 10 commonly misspelled words?

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!