noun, plural stand·bys.
- a staunch supporter or adherent; one who can be relied upon.
- something upon which one can rely and therefore choose or use regularly.
- something or someone held ready to serve as a substitute, especially a radio or television program used as a filler in case of cancellation of a regularly scheduled program.
- a traveler who is waiting for last-minute accommodations to become available on a plane, train, or other transport as a result of a cancellation.
- kept readily available for use in an emergency, shortage, or the like: a standby player.
- of or relating to last-minute accommodations, the transport that offers them, or a traveler who is waiting for them: a standby flight.
- of or relating to a waiting period.
- on standby, in a state of readiness to act, respond, or be used immediately when needed.
Ready and waiting, as in We’ve got three more painters on standby. This expression originated in the navy in the 1940s, where it referred to someone being ready to come on duty as soon as required. From about 1960 it began to be widely used in aviation for a passenger waiting to take the first available seat on a full flight.