Synonyms: standby
Definition: something that can be relied on when needed
Synonyms: understudy, standby
Definition: an actor able to replace a regular performer when required
Similar words: actor, histrion, role player, thespian, player
Definition: a theatrical performer
Synonyms: standby
Definition: ready for emergency use
Usage: a standby generator; a standby crew
Similar words: secondary
Definition: being of second rank or importance or value; not direct or immediate
Usage: the stone will be hauled to a secondary crusher; a secondary source; a secondary issue; secondary streams