flatline

An asystole; the absence of heart contractions or brain waves.

Noun

An asystole; the absence of heart contractions or brain waves.
1. The disappearance of the rhythmic peaks displayed on a heart monitor.
2. The disappearance of brain waves on an electroencephalogram.
  - When brain function ceases, the electroencephalogram shows flatline recordings. - 1972, Louis Lasagna, “Aging and the field of medicine”, in Matilda White Riley, Anne Foner, editors, Aging and Society: Aging and the...
An unchanging state, as indicated in a graph of a variable over time.
- Thus, you hear words like "flatline recession," "improvement at a greatly reduced rate," "economic hiccup," "recessionette," "rolling readjustment" and "the economy is double clutching." - 1967 June 17, “Business...
A line that is run low to the water from the rod tip, generally off a release clip of some type.

From flat + line. Refers to a continuous straight line (asystole) on an ECG (EKG) or EEG, indicating death.

To stop beating.
To die.
To kill.
- If looks could kill, Mona's sharp gaze would have flatlined him in one second. - 2013, Shobha Nihalani, Nine:
- After all she'd been through, she needed sleep and food to heal, not endure a lovemaking session that was so passionate that it had pretty much flatlined him as well. - 2017, Stephanie Rowe, Not Quite Dead:
To remain at the same level, without development; or, to fall.
- The economy in Northern Ireland is flatlining and jobs are scarce. - 2012, The Guardian, National Trust attempts to block £100m Giant's Causeway golf course:
- But passenger numbers have since recovered to only 85% of pre-March 2020 levels, and growth has flatlined. - 2022 November 16, Mel Holley, “Network News: West Midlands prioritises the return of passsengers”, in RAIL,...
To experience significantly decreased rates of change compared to previous rates of change.
- Upon upload, the video got 1,000 views/day for the first week, then flatlined and started getting fewer than ten views/day.
To fish using a flatline.