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verb (intransitive) (informal)
to die or be so near death that the display of one's vital signs on medical monitoring equipment shows a flat line rather than peaks and troughs
to remain at a continuous low level
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
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Contemporary definitions for flatline

to die

See flatline

Word Origin

from the flat line displayed on a heart monitor when the heart stopped functioning

Usage Note

slang; also flatline n.'s 21st Century Lexicon
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Word Origin and History for flatline

by 1998, from the flat line on an electrocardiogram or electroencephalogram when the patient is dead. Related: Flatlined; flatlining.

Online Etymology Dictionary, © 2010 Douglas Harper
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Slang definitions & phrases for flatline



Dead: The defendant's face was flatline


To die: State government is in a coma. We're going to flat-line at any moment

[1980s+; fr the flat line showing no waves, hence no heartbeat, on a heart-monitoring machine]

The Dictionary of American Slang, Fourth Edition by Barbara Ann Kipfer, PhD. and Robert L. Chapman, Ph.D.
Copyright (C) 2007 by HarperCollins Publishers.
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