Synonyms of lethal

lethal

adjective

ˈlē-thəl 

as in deadly

likely to cause or capable of causing death

we were lucky that the snake's venom wasn't lethal, and our friend turned out to be all right

Synonyms & Similar Words

• deadly
• fatal
• poisonous
• infectious
• infective
• killer
• harmful
• toxic
• dangerous
• murderous
• deathly
• terminal
• mortal
• destructive
• baleful
• hazardous
• injurious
• vital
• fell
• deleterious
• pernicious
• pestilent
• virulent
• baneful
• risky
• noxious
• sublethal
• serious
• perilous
• pestilential
• threatening
• menacing
• truculent
• ugly
• bloody
• unhealthy
• sanguinary
• grievous
• grave
• parlous
• unsound
• sanguine
• jeopardizing
• internecine

Antonyms & Near Antonyms

• healthy
• nonlethal
• beneficial
• healthful
• nonfatal
• wholesome
• salutary
• salubrious
• restorative
• curative
• corrective
• useful
• remedial
• advantageous
• tonic
• safe
• nontoxic
• alleviative
• nonpoisonous

Synonym Chooser

How does the adjective lethal differ from other similar words?

Some common synonyms of lethal are deadly, fatal, and mortal. While all these words mean "causing or capable of causing death," lethal applies to something that is bound to cause death or exists for the destruction of life.

lethal gas

When is deadly a more appropriate choice than lethal?

The words deadly and lethal can be used in similar contexts, but deadly applies to an established or very likely cause of death.

a deadly disease

When could fatal be used to replace lethal?

Although the words fatal and lethal have much in common, fatal stresses the inevitability of what has in fact resulted in death or destruction.

fatal consequences

When might mortal be a better fit than lethal?

While in some cases nearly identical to lethal, mortal implies that death has occurred or is inevitable.

a mortal wound

Example Sentences

Recent Examples of lethal

Re-establishing prisons and detention centers in these same buildings means placing detainees into spaces that have been proven to be lethal, regardless of the agency now running these sites. —Amer Matar, The Dial, 26 May 2026

According to local media reports, Xu spent hundreds of thousands of yuan (tens of thousands of dollars) to buy highly toxic substances online, including alpha-amanitin, a lethal compound found in some poisonous mushrooms. —ABC News, 26 May 2026

Cold-water releases can also help prevent rivers from heating up to lethal temperatures during critical spawning, rearing and migration periods. —Eric Palkovacs, The Conversation, 26 May 2026

Spencer, 74, is scheduled to die by lethal injection on June 25 at Florida State Prison in Starke, according to the warrant. —Jim Turner, Sun Sentinel, 26 May 2026