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

• check out
• conk (out)
• croak [slang]
• decease
• demise
• depart
• die
• drop
• end
• exit
• expire
• fall
• go
• kick in [slang]
• kick off [slang]
• part
• pass (on)
• pass away
• peg out [chiefly British]
• perish
• pop off
• step out
• succumb

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

Growth had been a fact of life in California and San Diego for decades, but the region's population flatlined in recent years as the high cost of living forced people out and challenged leaders to tell a new story of the local economy. —Andrew Keatts, Axios, 17 Mar. 2025

The Electric State, which boasts quite a sprawling cast of big names including Chris Pratt and Millie Bobby Brown, is flatlining with critics (17%) but audiences seem to be enjoying the post-apocalyptic sci-fi movie a lot more (69%) and it’s bound to be a big hit on Netflix. —Erik Kain, Forbes, 14 Mar. 2025

Three college students helped save a fellow student who flatlined three times, according to reports. —Sam Gillette, People.com, 14 Mar. 2025

Bosch struggles in Germany’s flatlining economy Bosch is one of Germany’s biggest employers, with a headcount of 429,000 people at the end of 2023, according to its latest annual report. —Byryan Hogg, Fortune Europe, 25 Nov. 2024

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