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 of flatline

• die
• fall

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 the disappointment of Die, My Love, another star vehicle from an auteur director that flatlined at theaters, the distributor needs a win. — Mia Galuppo, HollywoodReporter, 23 June 2026

For the past decade, the British economy has flatlined, while its population has become older, sicker, and no more productive. — Sam Knight, New Yorker, 22 June 2026

Specifically, the Xbox Series generation appears to be close to flatlining. — Paul Tassi, Forbes.com, 11 June 2026

Our modern dating culture has completely distorted that distinction and our relationships are flatlining because of it. — Sabrina Romanoff, CNBC, 5 June 2026

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
• brucine
• byline

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