flatline /ˈflætˌlaɪn/verb 6noun 5forms 3 verb6 •To stop beating. •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. •(informal) To remain at the same level, without development; or, to fall.The economy in Northern Ireland is flatlining and jobs are scarce. — 2012 •To die. •(slang) To kill.If looks could kill, Mona's sharp gaze would have flatlined him in one second. — 2013 •To fish using a flatline. noun5 •An asystole; the absence of heart contractions or brain waves. •The disappearance of the rhythmic peaks displayed on a heart monitor. •The disappearance of brain waves on an electroencephalogram.When brain function ceases, the electroencephalogram shows flatline recordings. — 1972 •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 •A line that is run low to the water from the rod tip, generally off a release clip of some type. formsflatlined · flatlining · flatlines