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

Chase Brown had completely flatlined as a fantasy commodity before Flacco’s arrival, and Tee Higgins was approaching a similar status. —Andy Behrens, New York Times, 17 Oct. 2025

So random though, and never had both my phone and internet just flatline like that. —James Bickerton, MSNBC Newsweek, 17 Oct. 2025

Every time the plot hits the reset button, the tension flatlines. —Justin Chang, New Yorker, 14 Oct. 2025

Fanning flatlines when left to be a solo show as Bertino whacks her around like a pinball, hitting big, loud scares that seem to keep resetting. —J. Kim Murphy, Variety, 11 Oct. 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