Origin of flatline; from flat + line: from earlier use as noun , for the unfluctuating readout line on a medical monitor, indicating a cessation of heartbeat
intransitive verbflat·lined, flat·lin·ing, flat·lines
- To show a horizontal line on a monitor indicating no electrical activity in an electrocardiogram or an electroencephalogram.
- Informal To die.
- To be in an unchanging condition: Participation in civic activities has flatlined in recent years.
(third-person singular simple present flatlines, present participle flatlining, simple past and past participle flatlined)
flatline - Investment & Finance Definition
A market that returns to where it opened, having neither a gain nor a loss. A chart of the market shows a line that looks flat. The term is used more frequently on financial television programs than in news articles or magazines.