Being, or having the nature of, a reserve or reserves
For use during emergencies:
Possessing some quality, or having been subject to some operation (as substitution), in the second degree; as, a secondary salt, a secondary amine, etc. Compare primary.
(Grammar) Relating to an auxiliary verb.
A performer who understudies.
The definition of supplementary is something that is added on, or that completes something.
Used or held in reserve
Find another word for standby. In this page you can discover 11 synonyms, antonyms, idiomatic expressions, and related words for standby, like: reserve, supplemental, backup, stand by, emergency, secondary, auxiliary, increase, understudy, timer and supplementary.