Longman Dictionary of Contemporary English
The Collaborative International Dictionary
Knell \Knell\, n. [OE. knel, cnul, AS. cnyll, fr. cnyllan to sound a bell; cf. D. & G. knallen to clap, crack, G. & Sw. knall a clap, crack, loud sound, Dan. knalde to clap, crack. Cf. Knoll, n. & v.] The stroke of a bell tolled at a funeral or at the death of a person; a death signal; a passing bell; hence, (figuratively), a warning or harbinger of, or a sound indicating, the passing away of anything; -- also called death knell.
The dead man's knell
Is there scarce asked for who.
--Shak.
The curfew tolls the knell of parting day.
--Gray.
death knell \death" knell`\, n.
A stroke or tolling of a bell, announcing a death; a knell[1].
Hence: (figuratively) A sign or harbinger of the end, death, or passing away of anything.
Wiktionary
alt. 1 The tolling of a bell announcing death. 2 (context idiomatic by extension English) A sign or omen foretelling the death or destruction of something. n. 1 The tolling of a bell announcing death. 2 (context idiomatic by extension English) A sign or omen foretelling the death or destruction of something.
WordNet
n. an omen of death or destruction
a bell rung to announce a death [syn: death bell]
Wikipedia
A death knell is the ringing of a bell to announce a death. This is also called tolling the bell.
The ancient custom of ringing a church bell at the actual time of death (the Passing-Bell, or rather the Death Knell) fell into disuse in England by the end of the 18th century. More customary at the end of the 19th century was to ring the Death Knell as soon as notice reached the clerk of the church or sexton, unless the sun had set, in which case it was rung at an early hour the following morning.
It was usual to repeat the knell early on the morning of the day when the funeral took place; but although canon law permitted tolling after the funeral there does not seem to be any record that this was practiced.
The manner of ringing the knell varied in different parishes. Occasionally the age of the departed was signified by the number of chimes (or strokes) of the bell, but the use of "tellers" to denote the sex was almost universal, and by far the greater number of churches in the counties of Kent and Surrey used the customary number of tellers, viz., three times three strokes for a man and three times two for a woman, with a varying use for children across the counties.
J C L Stahlschmidt produced comprehensive lists of the practices at each church in Kent and Surrey in his two volumes. Transcriptions of the books have been produced by Robarts – University of Toronto.
The term "death knell" is also used as a metaphor to describe an event or thing that brings about the "death" of another entity, or to signal that the death has taken place.
Usage examples of "death knell".
Excited shouts, cold death knell of iron, boots pounding for the doorway!
I counted, and with each numeral there came a sort of shudder, as if it had been a death knell.
They had rung the bells when King Robert died, she remembered, but this was different, no slow dolorous death knell but a joyful thunder.
Gotaro's voice sounded like a death knell to Nangi as his gaze followed his friend's lead.
His manner was so casual when he was sounding the death knell of Tara.