A course of inquiry that leads nowhere.
Used other than figuratively or idiomatically: see blind, alley. A street or passageway that leads nowhere.
A thing or occurrence which initially causes fear, distress, etc. but which is subsequently recognized as being no cause for concern.
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.