Definition of

Knell

(noun, event) the sound of a bell rung slowly to announce a death or a funeral or the end of something
(verb, perception) make (bells) ring, often for the purposes of musical edification
My uncle rings every Sunday at the local church
(verb, perception) ring as in announcing death

via WordNet, Princeton University

Synonyms of Knell

Derivations: knell

Hyponyms: toll

Hypernyms: bell, peal, ring, sound, toll

O.E. cnyll "sound made by a bell when struck or rung slowly," of imitative origin. Cf. M.H.G. erknellen "to resound," O.E. cnyllan. The Welsh cnull "death-bell" appears to be a borrowing from Eng. For vowel evolution, see bury.

baltimore311 Opened Trash, High Grass, or Weeds request via Android at 5614 knell Ave Baltimore http://t.co/ltxaVtIy. A mess of overgrowth.
ComradeArthur RT @rsmccain: Ding-dong, the witch is dead! #tcot RT @AmPowerBlog Old media death knell: L.A. Times Magazine is Shutting Down http://t.co/4v6mpWWs
Knell_xx というか、梵天にもふもふしたい。
jsudie Am I the only one who thinks Facebook going public is the death knell of it? #forwhomthebelltolls