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

Some were involved in surveillance, several were guiding lethal drones from the safety of their Tel Aviv headquarters, and others were on the ground. — Jay Weissberg, Variety, 10 Sep. 2026

The atmosphere is a near-vacuum, radiation is lethal, and temperatures plunge to soul-crushing lows. — Mrigakshi Dixit, Interesting Engineering, 10 Sep. 2026

She had been born with a condition called Amish lethal microcephaly that causes an unusually small head and underdeveloped brain. — CBS News, 10 Sep. 2026

In the series, four very different women learn to survive on a lethal tropical island after their mining exec husbands are kidnapped. — Matt Grobar, Deadline, 9 Sep. 2026