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

Prices flatlined last summer but have risen at a 4.5% annual rate over the last three months, far above the Fed's goals and the highest since fall 2022. —Courtenay Brown, Axios, 12 Feb. 2025

The economy flatlined in the third quarter, according to data released in December, while the latest monthly GDP reading showed the economy expanded just 0.1% in November, after shrinking by 0.1% in October. —Sophie Kiderlin, CNBC, 6 Feb. 2025

Ford flatlined twice and underwent a 10-hour surgery before being placed on an extracorporeal membrane oxygenation (ECMO) machine for a week. —Eileen Finan, People.com, 5 Feb. 2025

Demand for new electric vehicles has flatlined in California, new sales figures show, raising questions as to whether automobile manufacturers can meet ambitious state mandates for zero-emission vehicle sales. —Russ Mitchell, Los Angeles Times, 4 Feb. 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