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

Sheridan's formidable character, Cody, is the most experienced (and vocal) at surviving this new, lethal style of warfare. — Bryan Alexander, USA Today, 2 Aug. 2026

Trout need cool water to survive, but record heat this summer has driven water temperatures to lethal levels for fish. — Matthew Brown, Fortune, 1 Aug. 2026

Record-breaking heat and drought are driving Western rivers to lethal temperatures for trout, forcing wildlife officials to impose widespread afternoon fishing closures in Montana and Colorado, including parts of Yellowstone park. — Matthew Brown, Los Angeles Times, 1 Aug. 2026

There were 28 records of physical attacks, at least 144 non-lethal poisoning episodes and 27 human fatalities resulting from consumption of the fish, the study found. — Teresa Mull, FOXNews.com, 1 Aug. 2026