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 sudden or unexpected failure.
A ludicrous or humiliating situation. Some effort that went quite wrong.
A wine bottle in a (usually straw) jacket.