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.

If left untreated, those conditions could become life-threatening.

From BBC • Jun. 8, 2026

Days later, he ended up in an emergency room, where medical testing later confirmed an E. coli infection that resulted in a life-threatening kidney complication, according to his attorney.

From Los Angeles Times • May 31, 2026

"If these findings are confirmed in Phase III trials, we may finally be able to offer patients a targeted therapy that halts and potentially reverses liver damage before it progresses to life-threatening stages."

From Science Daily • May 27, 2026

Three doctors gathered and told the couple that the longer Waldorf’s cervix remained open and her uterus exposed to bacteria, the higher her risk of developing a life-threatening infection.

From Salon • May 27, 2026

Dad was watching baseball, Mom was working on her laptop, and I was experiencing a life-threatening level of boredom.

From "Klawde: Evil Alien Warlord Cat" by Johnny Marciano and Emily Chenoweth