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: understudy, alternate
Definition: be an understudy or alternate for a role
Similar words: con, learn, memorise, memorize
Definition: commit to memory; learn by heart
Usage: Have you memorized your lines for the play yet?