standby
noun [ C ] uk/ˈstænd.baɪ/ us/ˈstænd.baɪ/ standbys
(READY)
（尤指为应对出现问题或故障时的）备用设备，备用品，替代物
something that is always ready for use, especially if a regular one fails
Board games are a good standby to keep the children amused if the weather is bad. 天气不好时，棋类游戏是个不错的哄孩子们开心的备用选择。
There are standby generators but these usually only have to work for a few hours a year during power cuts. 有备用发电机，不过通常一年只在断电时使用几个小时。
on standby 待命；备用；随时准备
When a person or a thing is on standby, they are ready to be used if necessary.
Hospitals are on standby ready to deal with casualties from the crash. 医院随时准备着接纳撞车事故的伤者。
(TICKET)
(also standby ticket)（航班起飞前或演出开始前廉价出售的）余票
a cheap ticket sold just before a flight or a performance if there is a seat available