false alarm

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false alarm (plural false alarms)

1. (literal) 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.
   • 1895, G. A. Henty, chapter 9, in Wulf the Saxon:

     "Then, if they rise, shout the alarm at the top of your voice [...] but be careful not to rouse the camp by a false alarm, for if you do, instead of gaining credit we shall become the jest of the whole force."

   • 2013 February 25, David Epstein, “Pistorius: The Man, The Myth”, in Sports Illustrated, retrieved 18 April 2015:

     Pistorius explained that a security alarm in his house had gone off the previous night, and that he had taken a gun downstairs to investigate what turned out to be a false alarm.

2. (idiomatic, by extension) A thing or occurrence which initially causes fear, distress, etc. but which is subsequently recognized as being no cause for concern.
   • 1819 December 20 (indicated as 1820), Walter Scott, chapter XIII, in Ivanhoe; a Romance. , volume I, Edinburgh: Archibald Constable and Co.; London: Hurst, Robinson, and Co. , →OCLC, page 265:

     "This may be a false alarm, or a forged letter," said De Bracy.

   • 1843 December 19, Charles Dickens, “Stave Two. The First of the Three Spirits.”, in A Christmas Carol. In Prose. Being a Ghost Story of Christmas, London: Chapman & Hall, , →OCLC, page 70:

     The terrible announcement that the baby had been taken in the act of putting a doll's frying-pan into his mouth, and was more than suspected of having swallowed a fictitious turkey, glued on a wooden platter! The immense relief of finding this a false alarm!

   • 1905, Fergus Hume, chapter 6, in The Secret Passage:

     Cuthbert had often been summoned to her dying bed, only to find that she was alive and well. He expected that this summons would be another false alarm.

   • 2000 January 9, “A Night To Remember”, in Newsweek, retrieved 18 April 2015:

     Robert Swanson [...] expected civilization to melt down on Jan. 1, 2000 [...] He's not sure yet that Y2K was a false alarm.

3. (archaic, idiomatic) A person who pretends to be more accomplished or a thing that seems to be of higher quality than is later found to be the case.

   Antonym: real deal

   • 1911, William MacLeod Raine, chapter 22, in Mavericks:

     "I don't believe you're a bank robber, at all! I don't believe you are even a rustler! You're a false alarm!"

   • 1912, G. Harvey Ralphson, chapter 2, in Boy Scouts in a Submarine:

     "He's an old false alarm, anyway. I'll bet he never heard a real gun go off!"

   • 1913, Rex Ellingwood Beach, chapter 5, in The Iron Trail:

     "I had a good job, putting in a power plant for his nibs"—he indicated the retreating Gordon with a disrespectful jerk of the thumb—"but I quit [...] Do you think I'd work for this four-flusher if you were in the country?" [...]
     "You think Gordon is a false alarm?"

   • 1921, P. G. Wodehouse, chapter 4, in Jill the Reckless:

     "I only came over here to see that darned false alarm of a play of mine put on."

• false positive

• “false alarm”, in OneLook Dictionary Search.