Definitions

life-threatening

[lahyf-thret-ning, -thret-n-ing] / ˈlaɪfˌθrɛt nɪŋ, -ˌθrɛt n ɪŋ /

ADJECTIVE

very dangerous

Synonyms

STRONGEST

deadly lethal mortal serious severe

WEAK

capital critical hazardous threatening touch and go unsafe

Antonyms

STRONGEST

harmless invigorating

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

A life-threatening brain swelling she experienced in response to her early immunotherapy would have made her ineligible for the treatment.

From The Wall Street Journal • May 14, 2026

While trying to use his bear spray canister, he sustained “significant but not life-threatening injuries to his chest and left arm,” according to officials.

From Los Angeles Times • May 8, 2026

Sepsis, which can be life-threatening and is difficult to spot, is an emergency reaction to infection where the immune system overcompensates and damages tissues and organs.

From BBC • Apr. 26, 2026

Eighteen percent reported that it led to a life-threatening event or required an intervention to prevent permanent harm.

From MarketWatch • Apr. 22, 2026

It was not life-threatening, as the rope-assisted passage across the cliff face had been.

From "Son" by Lois Lowry