flatline

verb

flat·​line ˈflat-ˌlīn 

flatlined; flatlining; flatlines

intransitive verb

1

a

: to register on an electronic monitor as having no brain waves or heartbeat

b

: die

2

a

: to be in a state of no progress or advancement

b

: to come to an end

flatliner noun

Synonyms

• die
• fall
• perish

Examples of flatline in a Sentence

the patient was fading fast, and doctors expected him to flatline before the night was over

Recent Examples on the Web

After flipping a first-possession interception by linebacker Zack Baun into a short-field touchdown, the Eagles offense flatlined under first-time offensive coordinator Kevin Patullo. —Brooks Kubena, New York Times, 22 Sep. 2025

After administering chest compressions — during which Bennett flatlined — a doctor asked if the couple would be willing to put their son on life support. —Greta Bjornson, PEOPLE, 21 Sep. 2025

Getty Images That upward trajectory stands in contrast to the United States, where life expectancy virtually flatlined during the 2010s and even dipped slightly on occasions during the 2010s—a trend blamed in large part on a surge in deaths from overdoses from the synthetic opioid fentanyl. —Micah McCartney, MSNBC Newsweek, 18 Sep. 2025

Once front-line teams stop trusting the data—or can't see how the tools help their day-to-day—the adoption curve flatlines. —Andy Watts, Forbes.com, 18 Sep. 2025

Word History

First Known Use

1980, in the meaning defined at sense 1a

Rhymes for flatline

• affine
• airline
• align
• aline
• assign
• baseline
• beamline
• benign
• bloodline
• bovine
• byline
• canine

Medical Definition

flatline

intransitive verb

flat·​line ˈflat-ˌlīn 

flatlined; flatlining

1

: to register on an electronic monitor as having no heartbeat or brain waves : to experience cessation of heart contractions or brain wave activity as indicated by a flat line on a electrocardiogram or electroencephalogram

I flatlined on the operating table, but Dr. Bunsom managed to revive me.

—Alison Wright, Yoga Journal

He used to be ill quite a bit as a younger child, and his heart flatlined four times before he was 6.

—Ginnie Graham, Tulsa World

2

: die entry 1

But just because death is expected doesn't mean it's any less depressing when the patient finally flatlines.

—Phil Taylor, Sports Illustrated