standbystand·by1 /ˈstændbaɪ/ (also stand-by) nounTRAVEL1[countableC] someone or something that is ready to be used when neededThe government has asked potential donor countries for 75,000 tonnes of grain as a standby.
2[uncountableU] when you are ready to travel on a plane, but can only do so if there are seats left when it is ready to leaveThe flight is full, but we can put you on standby.