A state of readiness without immediate involvement; remaining in preparation for (a sudden or unforeseen event or situation).
The troops were on standby in case of an attack.
In 1915, concurrent with the L.S.W.R. electrification, power was supplied from the Waterloo sub-station, and the old equipment held in reserve. Some generator sets were removed, and motor generators installed for standby lighting and other services.1958 August 23, T. S. Lascelles, “Diamond Jubilee of the Waterloo & City Railway”, in Railway Magazine, page 523:
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A replacement kept on standby.
During three weeks of the run, I was performing with walking pneumonia, but I had no choice other than to perform because we didn't have the budget for stand-bys.1977 December 17, Harold Pickett, quoting Jim Ferguson, “New York, New York”, in Gay Community News, volume 5, number 24, page 6:
Lifestyle, Tourism, Transport, Travel Waiting at the airport in the hope of getting a seat on a flight that is already booked out.
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Something that is standard, well-tested, or frequently used.
That recipe is an old standby, and she keeps the ingredients around in case of unexpected guests.
The restaurant, Hop Louie, was a Chinatown standby for decades before closing in 2016.2022 March 2, Erin Woo, Kevin Roose, “This Social Club Runs On Crypto Tokens and Vibes”, in The New York Times, →ISSN, archived from the original on 22 Mar 2023:
1 more example
Emerging from an Everyman Espresso shop in Park Slope, Brooklyn, last month, David Lieber, a customer, lamented what he saw as Blank Street’s targeting of a neighborhood standby.2022 August 29, Julia Moskin, “It’s Not Just You — Blank Street Coffee Is Suddenly Inescapable”, in The New York Times, →ISSN, archived from the original on 01 Feb 2023: