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

One potential data point indicating this possibility is recent Commerce Department figures showing growth in proprietors’ income—a proxy for small businesses—flatlining in May. —Irina Ivanova, Fortune, 13 July 2025

Despite huge progress in treatment access — now reaching nearly 30 million people — HIV prevention has flatlined. —Peter Sands, Forbes.com, 9 July 2025

Even as major companies pare back or flatline diversity commitments, a few, including Costco and Cisco, have publicly defended DEI. —Jessica Guynn, USA Today, 19 May 2025

For the city’s bars, the number of liquor licenses has flatlined in recent years, according to Pat Doerr, director of the Hospitality Business Association of Chicago. —Jake Sheridan, Chicago Tribune, 23 June 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