|death knell or death bell|
|1.||something that heralds death or destruction|
|2.||a bell rung to announce a death|
|death bell or death bell|
|an extraordinary or unusual thing, person, or event; an exceptional example or instance.|
|an arrangement of five objects, as trees, in a square or rectangle, one at each corner and one in the middle.|
Something that indicates impending failure, as in His low scores sounded the death knell for his ambitions. The noun knell, used for the ringing of a bell since at least a.d. 1000, is rarely heard today except in this figurative phrase.