Flatline
/ˈflætˌlaɪn/noun
A nearly horizontal line on a medical monitor indicating no detectable heartbeat or brain activity; by extension, to decline to zero or stop functioning.
Did you know?The medical sense is a 20th-century coinage from the literal line drawn across an electrocardiogram or monitor, and it later spread into slang for anything that suddenly goes dead or stops performing.
Etymological Timeline
Old English
OE
flæt
“level, even, not raised”
Old English
OE
līne
“a cord, rope, or marked line”
Late 19th Century
English
flat line
“a horizontal line, especially in technical or graphing contexts”
20th Century
English
flatline
“a medical monitor trace showing no detectable pulse or electrical activity”
Modern English
English
flatline
“to fail, stop, or drop sharply to zero”