flatline

noun

1. An unchanging state, as indicated in a graph of a variable over time.

2. Asystole; the absence of heart contractions or brain waves.

3. The disappearance of the rhythmic peaks displayed on a heart monitor.

4. The disappearance of brain waves on an electroencephalogram.

verb

1. (intransitive, of the heart) To stop beating.

2. (intransitive, by extension) To die.

3. To stay at the same level, without development; or, to fall.