A warning signal (such as the call of sentry, the ringing of a bell, or the shriek of a siren) which turns out to have been given erroneously.
A thing or occurrence which initially causes fear, distress, etc. but which is subsequently recognized as being no cause for concern.
A road with no exit; a cul-de-sac.
A deadlock or stalemate situation in which no progress can be made.