lethal

1 of 2

adjective

le·​thal ˈlē-thəl 

1

a

: 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

lethality

lē-ˈtha-lə-tē 

noun

lethally

ˈlē-thə-lē 

adverb

lethal

2 of 2

noun

1

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

2

: lethal gene

Synonyms

Adjective

• deadly
• fatal
• poisonous

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

Wuornos, who was found guilty of six murders and received six death sentences, was executed by lethal injection on October 9, 2002, after a decade on death row. —Jason Pham, StyleCaster, 31 Oct. 2025

Wuornos was executed by lethal injection in October 2002, according to a New York Times obituary. —Allison Degrushe, Entertainment Weekly, 31 Oct. 2025

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

Word History

Etymology

Adjective and Noun

Latin letalis, lethalis, from letum death

First Known Use

Adjective

circa 1604, in the meaning defined at sense 1a

Noun

1917, in the meaning defined at sense 1

Phrases Containing lethal

• lethal gene

Rhymes for lethal

• nonlethal
• sublethal

Kids Definition

lethal

1 of 2 adjective

le·​thal ˈlē-thəl 

: causing or capable of causing death

lethal chemicals

lethally

ˈlē-thə-lē 

adverb

lethal

2 of 2 noun

: lethal gene

Medical Definition

lethal

1 of 2 adjective

le·​thal ˈlē-thəl 

: of, relating to, or causing death

a lethal injury

also : capable of causing death

lethal chemicals

a lethal dose

lethality

lē-ˈthal-ət-ē 

noun

plural lethalities

lethally adverb

lethal

2 of 2 noun

1

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

2

: lethal gene