n.
Function: adjective
Date: 1872
1 : held near at hand and ready for use <a standby power plant> < standby equipment>
2 : relating to the act or condition of standing by < standby duty> <a standby period>
3 : of, relating to, or traveling by an airline service in which the passenger must wait for an available unreserved seat < standby passengers> <a standby ticket>