standby

or stand-by

[ stand-bahy ]
/ ˈstændˌbaɪ /

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.

adjective

Idioms for standby

    on standby, in a state of readiness to act, respond, or be used immediately when needed.

Origin of standby

First recorded in 1790–1800; noun, adj. use of verb phrase stand by

Example sentences from the Web for standby