Syncope

noun

1. The loss or elision of a sound from the interior of a word, for example by changing cannot to can't, never to ne'er, or the pronunciation of the -cester ending in placenames as -ster (for example, Leicester pronounced Leister or Lester, and Worcester pronounced Wooster).
2. A loss of consciousness when someone faints, a swoon.
3. A missed beat or off-beat stress in music resulting in syncopation.