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

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

At its Premier Inn hotel division – which is responsible for almost three-quarters of group turnover – sales flatlined in the three month period due to enduring weakness in its home territory. —Royston Wild, Forbes.com, 19 June 2025

Despite having studied in the United States, her job prospects have flatlined ever since switching careers. —Siddhant Adlakha, Variety, 17 June 2025

Behind the failing units and flatlined comps lie brands with real equity, untapped assets, and inefficient structures screaming for reinvention. —Jim Osman, Forbes.com, 19 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