flat line

Noun

flatline (plural flatlines)

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 professions, page 68
3. (also, figuratively) 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 Outlook”, in Business Week, part 6, page 23
4. A line that is run low to the water from the rod tip, generally off a release clip of some type.

See all 10 meanings of flatline