Merriam-Webster Collegiate Dictionary - knell

 I. verb  Etymology: Middle English, from Old English cnyllan; akin to Middle High German er~en to toll  Date: before 12th century  transitive verb to summon or announce by or as if by a ~  intransitive verb  1. to ring especially for a death, funeral, or disaster ; toll  2. to sound in an ominous manner or with an ominous effect  II. noun  Date: before 12th century  1. a stroke or sound of a bell especially when rung slowly (as for a death, funeral, or disaster)  2. an indication of the end or the failure of something sounded the death ~ for our hopes