stand-by

noun

1. 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.”
2. Sleep mode
3. (travel) Waiting at the airport in the hope of getting a seat on a flight that is already booked out.
4. 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.”