Un"der*stud`y (?), v. t. & i. (Theater) To study, as another actor's part, in order to be his substitute in an emergency; to study another actor's part.

Un"der*stud`y, n. One who studies another's part with a view to assuming it in an emergency.

Un"der*stud`y (?), v. t. & i. (Theater) To study, as another actor's part, in order to be his substitute in an emergency; to study another actor's part.

Un"der*stud`y, n. One who studies another's part with a view to assuming it in an emergency.

• to study or know a role to such an extent as to be able to replace the normal performer when required
  
• to act as an understudy (to someone)
  
• a performer who understudies; a standby