Definitions

1. noun

A person who learns and performs the parts of a play, film, or other performance in case the main actor is unable to continue

“The understudy for the lead actress stepped in when she fell ill during the performance.”

2. verb

To learn and practice the parts of a role in case the main actor is unable to continue

“The actress had to understudy the lead role for the next three weeks, just in case.”

3. verb

To take over the role of someone who is unable to continue, especially in a performance

“The understudy had to understudy the lead role for the next three weeks, just in case, and then she understudied when the lead fell ill.”